UNIVERSITY  OF  CALIFORNIA 
AT   LOS  ANGELES 


THE  GIFT  OF 

MAY  TREAT  MORRISON 

IN  MEMORY  OF 
ALEXANDER  F  MORRISON 


THE    TEMPLE    PRIMERS 

FORMING 

An  International  Primer- 
Cyclopaedia 


\  SERIES  of  small  volumes  of  condensed  informa- 
f*"  tion  introductory  to  great  subjects,  written  by 
leading  authorities,  adapted  at  once  to  the  needs  of 
the  general  public,  and  forming  introductions  to 
the  special  studies  of  scholars  and  students. 

The  aim  of  the  Publishers  is  to  provide,  in  a  con- 
venient and  accessible  form,  the  information  which 
the  usual  bulky  and  high-priced  encyclopaedias  place 
beyond  the  easy  reach  of  the  average  reader.  The 
Series  will  accordingly  aim  at  the  comprehensive 
inclusion  of  the  chief  departments  of  Literature, 
Science,  and  Art,  and  it  is  fully  hoped  that  the 
volumes  will  form  a  complete  and  trustworthy 
Primer  -  Cyclopaedia  of  modern  knowledge. 

By  making  the  books  International,  the  Publishers 
hope  to  call  to  their  aid  the  most  distinguished  men, 


at  home  and  abroad,  belonging  to  the  great  Republic 
of  Learning — scholars  specially  identified  with  various 
branches  of  knowledge. 

Among  English  scholars  who  have  kindly  con- 
sented to  help  in  the  scheme  may  be  mentioned  the 
following  : 

The  Right  Hon.  Leonard  Courtney,  M.P.,  will 
write  on  The  English  Constitution  ;  Mr.  Henry 
Bradley,  Joint-Editor  of  the  "New  English  Dic- 
tionary," on  The  Making  of  English;  Dr.  Hill, 
Master  of  Downing  College,  late  Vice -Chancellor 
of  the  University  of  Cambridge,  will  contribute  An 
Introduction  to  the  Study  of  Science ;  Professor 
E.  Jenks,  Reader  in  Law  to  the  University  of  Oxford, 
A  History  of  Politics;  Mr.  Israel  Gollancz,  An 
Introduction  to  Shakespeare;  The  Very  Rev.  H. 
D.  M.  Spence,  Dean  of  Gloucester,  will  deal  with 
The  English  Church;  Dr.  Henry  Sweet,  The 
History  of  Language  ;  Professor  William  Ramsay, 
F.R.S.,  etc.,  the  Joint  Discoverer  of  Argon,  will 
write  a  text -book  on  Modern  Chemistry;  Mr. 
George  R.  Parkin,  G.C.M.G.,  the  great  Imperialist, 
will  write  on  The  British  Empire ;  Mr.  Romesh 
C.  Dutt,  C.I.E.,  Lecturer  in  Indian  History,  Uni- 
versity College,  London,  The  Civilisation  of  India; 
Mr.  Basil  Worsfold,  M.A.  (Oxon.),  Author  of  "The 
Principles  of  Criticism,"  will  treat  Literary  Criti- 
cism; Mr.  Edmund  Gardner,  M.A.  (Camb.), 
Author  of  "Dante's  Paradise,"  will  prepare  A  Gen- 
eral Introduction  to  Dante;  Mr.  L.  D.  Barnett, 
M.A.  (Camb.),  Assistant -Keeper  of  Oriental  MSS., 


British  Museum,  will  survey  the  History  of  The 
Greek  Drama,  etc. 

The  Publishers  have  been  fortunate  enough  to 
secure  the  help  of  M.  Gaston  Paris,  Member  of  the 
French  Academy,  Director  of  the  College  de  France, 
the  greatest  living  authority  on  Romance  Literature, 
for  a  book  on  Medieval  French  Literature,  and  it 
is  hoped  that  Professor  Villari  will  contribute  a 
Primer  on  The  Italian  Renaissance ;  while  in 
Germany  they  have  entered  into  close  relationship 
with  Messrs.  Goschen  with  reference  to  their  allied 
scheme  of  Science  and  other  Primers,  prepared  by 
recognised  educational  experts,  so  extensively  used  in 
German  High  Schools  and  Universities,  and  popular 
throughout  the  whole  country.  Among  the  German 
writers  whose  works  will  appear  in  The  Interna- 
tional Primer  Series  will  be  Doctors  Rebmann 
and  Seiler  on  The  Human  Frame  and  Laws  of 
Health  ;  Dr.  Dennert  on  Plants,  their  Structure 
and  Life ;  Dr.  Homes  on  Primitive  Man ;  Dr. 
Hommell  on  The  Civilisation  of  the  East;  Dr. 
M.  Haberlandt  on  The  Races  of  Mankind;  Dr. 
Koch  on  Roman  History ;  Dr.  Kaufmann  on 
Teutonic  Mythology;  Dr.  Rein  on  Educational 
Methods  ;  etc. 

The  above  lists  may  be  taken  as  fairly  illustrating 
the  wide  range  to  be  covered  by  the  Series,  and  it 
is  intended  that  no  branch  of  knowledge  will  be 
left  uncatered  for  when  the  library  is  completed. 

The  books  will  be  illustrated  with  the  necessary 
reproductions,  diagrams,  and  charts;  and  the  Pub- 


Ushers  will  do  everything  that  clear  print,  tasteful 
"get  up,"  and  low  price  can  effect  to  gain  the 
appreciation  of  all  classes  of  the  public. 

The   following  volumes  are  now  ready  or  nearing 
completion,  and  will   be  published  at  short  intervals: 

1.  AN  INTRODUCTION  TO  SCIENCE. 

By  Dr.  ALEXANDER  HILL,  Master  of  Downing  College,  Cambridge. 

2.  A  HISTORY  OF  POLITICS. 

By  Prof.  E.  JENKS.  M.A.,  Reader  in    Law  to  the   University  of  Oxford, 

3.  THE  ENGLISH  CHURCH. 

By  the  Very  Rev.  H.  D.  M.  SPENCE,  Dean  of  Gloucester. 

4.  ROMAN  HISTORY. 

By  Dr.  JULIUS  KOCH. 

5.  SOUTH  AFRICA. 

By  VV.  BASIL  WORSFOLD,  Author  of  "The  Story  of  South  Africa,"  "The 
Redemption  of  Egypt,"  etc. 

6.  THE  HISTORY  OF  LANGUAGE. 

By  HENRY  SWEET,  M.A.,  Author  of  "An  Anglo-Saxon  Reader,"  "Prin- 
ciples of  Language,"  etc.,  etc. 

7.  DANTE. 

By  EDMUND  G.  GARDNER,  M.A.  (Camb.),  Author  of  "Dante's  Paradise," 
etc. 

8.  THE     HUMAN     FRAME    AND    THE     LAWS     OF 

HEALTH. 

By  Drs.   REB.MANN  and   SEILER,  Professors   in    the  University   of   Lau- 
sanne. 

9.  THE  CIVILISATION  OF  INDIA. 

By  ROMESH  C.  DUTT,  M.A.,  Lecturer  at  University  College,  Translator 
and  Editor  of  the  "Mahabharata"  and  the  "  Ramayana." 

10.  THE  GREEK  DRAMA. 

By  LIONEL  D.  BARNETT,  M.A.  (Camb.),  Assistant-Keeper  of  the  Orien- 
tal  MSS.,  British  Museum. 

11.  THE  ENGLISH  CONSTITUTION. 

By  the  Rt.  Hon.  LEONARD  COURTNEY,  M.P. 

12.  THE  RACES  OF  MANKIND. 

By  Dr.  MICHAEL  HABERLANDT,  Curator  of  the  Ethnological    Museum, 

13.  MODERN  CHEMISTRY. 

By  Professor  WILLIAM  RAMSAY,  F.R.S. 


THE  TEMPLE  PRIMERS 


SOME   PROBLEMS    OF  THE   DAY 

IN    NATURAL    SCIENCE: 

AN   INTRODUCTION 

BY   ALEX.  HILL,  M.A.,   M.D., 

Master   of    Downing    College,    Cambridge 


LORD    LISTER,   P.  R.  S. 

From   a  photograph   fry    Kar rands 


IRTRODUCTIOR 
SCIEOCE 


COPYRIGHT,  1900 
BY  THE  MACMILLAN  COMPANY 


6$ount   Dleaaant 

J.  Horace  McFarland  Coi 
Harrisburg.  Pa. 


PREFACE 

THIS  little  book  aims  at  giving  an  account  in  popular 
language  of  the  scientific  problems  which  are  most  prom- 
inent at  the  present  time,  and  attempts  to  portray  the 
attitude  of  mind  of  those  who  are  engaged  in  solving 
them.  It  has  small  claim  to  the  title  An  Introduction  to 
Science.  If  it  serves  to  give  definiteness  to  the  general 
impressions  of  any  amateurs  of  science  who  have  attended 
meetings  of  the  various  learned  societies  during  the  last 
few  years,  its  object  will  be  fully  accomplished. 

Since  Bacon  wrote  his  Novum  Organum  and  Whewel 
issued  it  "Renovatum,"  the  field  of  science  has  extended 
until  it  is  no  longer  possible  for  any  single  student  to 
survey  it.  Hardly  can  we  hope  that  a  second  Herbert 
Spencer  will  extract  the  principles  from  all  its  provinces 
that  he  may  blend  them  into  a  new  philosophy. 

If  read  without  previous  training  or  subsequent  study, 
this  book  can  hardly  fail  to  be  misleading ;  but  it  is 
intended  as  an  introduction  to  a  series  of  Primers  in 
which  competent  teachers  will  treat  in  sufficient  detail  the 
problems  of  which  I  have  attempted  a  bird's-eye  view. 

ALEX.    HILL. 

DOWNING  LODGE, 

December,  1899. 

(v) 


TABLE   OF   CONTENTS 

SECTION   I— FIRST   PRINCIPLES 

PAGE 

DEFINITION  OF  SCIENCE i 

AIM  OF  SCIENCE 5 

BOUNDARIES  OF  SCIENCE n 

THE  RELATION  OF  PHILOSOPHY  TO  SCIENCE 25 

THE  SENSES  THE  AGENTS  OF  THE  MIND 29 

THE  EXTENSION  OF  THE  SENSES  BY  ARTIFICIAL  AIDS  .  .  40 

CLASSIFICATION  OF  THE  SCIENCES 45 

HISTORY  OF  SCIENCE 49 

METHOD  OF  SCIENCE 53 

SECTION   II— CERTAIN   PROBLEMS   OF  THE   DAY 

THE  AGE  OF  THE  EARTH 63 

THE  ULTIMATE  CONSTITUTION  OF  MATTER 74 

THE  ORIGIN  OF  SPECIES 90 

THE  CAUSE  OF  THE  COAGULATION  OF  BLOOD 105 

THE  FUNCTION  OF  NERVE-FIBRES  AND  NERVE-CELLS  .  .  115 

MlCROPHYTOLOGY  129 


(vii) 


LIST   OF   ILLUSTRATIONS 

LORD  LISTER Frontispiece 

LORD  BACON Facing  page  52 

LORD  KELVIN "         "      63 

THE  HON.  ROBERT  BOYLE "          "      74 

CHARLES  DARWIN "         "      90 

SIR  CHARLES  BELL "         "    115 


(viii) 


AN   INTRODUCTION  TO   SCIENCE 

SECTION    I 

CHAPTER  I 
First   Principles 

Definition  of  Science.— "  Definitions  might  be  good 
if  words  were  not  used  in  making  them,"  is  Rousseau's  well- 
known  paradox.  Before  any  form  of  words  can  be  found 
which  will  convey  to  the  mind  an  idea  of  the  meaning  of 
science,  the  words  themselves  must  be  defined.  Yet  every- 
one knows  what  the  expression  science  means,  and  appre- 
ciates its  value  as  an  amplification  of  the  term  knowledge. 
The  idea  of  science  as  it  hovers  in  the  atmosphere  of  the 
mind  has  significance,  difficult  as  it  is  to  pin  it  down  in  words. 
"Science  is  knowledge  reduced  to  law  and  embodied  in 
system."  The  phrase  sounds  explanatory,  yet  each  of  its 
terms  might  be  challenged  ;  and  it  might  well  be  asked 
whether  our  knowledge  is  reduced  to  law  because  our 
thoughts  about  the  things  we  know  are  arranged  in  order 
in  our  minds.  It  might  be  pointed  out  that  the  force  of 
the  phrase  is  extrinsic  rather  than  intrinsic,  proportional  not 
to  its  lucidity  but  to  the  experience  of  the  individual  using  it 
of  the  applications  of  the  word  law,  and  his  acquaintance 
with  systems  of  philosophy.  A  definition  should  be  at  the 
same  time  an  explanation;  but  the  concise  forms  of  words  in 
which  we  attempt  to  define  our  mental  conceptions  resemble 
more  frequently  the  analytical  titles  which  the  authors  of  the 
last  century  affected  for  their  books.  A  formula  does  not 
necessarily  inform.  It  may  limit  without  elucidating,  and 

A  (I) 


2  AN   INTRODUCTION   TO    SCIENCE 

."often  it  carries  but  little  information  to  those  who  have 
.not  already  a  considerable  acquaintance  with  the  subject. 

Science  is  a  synonym  of  knowledge  ;  but  a  synonym 
which  cannot  be  dispensed  with,  for  it  implies  knowledge 
of  a  particular  kind.  It  implies  not  only  an  acquaintance 
with  phenomena,  but  a  further  knowledge  of  their  simi- 
larity and  dissimilarity.  It  implies  a  sense  of  relation  and 
proportion  among  facts.  ''The  professor's  head  is  simply 
packed  with  facts  !  "  ''Yes,"  was  the  quiet  rejoinder,  "and 
they  are  all  of  exactly  the  same  size."  Science  is  knowledge 
in  perspective.  It  is  knowledge  viewed  down  the  vista  of 
time :  not  an  aggregation  of  facts  presented  simultaneously 
to  the  intellect,  but  a  sequence  of  facts  successively  ascer- 
tained and  placed  in  proper  relation  with  all  that  was 
previously  known.  Science,  therefore,  connotes  not  an 
acquaintance  with  facts  merely,  but  also  the  habit  of  drawing 
inferences,  the  mental  training  which  enables  the  observer 
to  link  data  together,  and  thus  to  make  them  fruitful  as 
materials  of  thought. 

Instead  of  seeking  for  a  pithy  expression,  which  at  the 
end  of  our  study  will  sum  up  its  purpose  and  by  denning 
the  word  "science"  remind  us  of  its  scope,  we  recognize 
that  the  word  ' '  science ' '  suggests  to  our  minds  the  pro- 
gressive accretion  of  knowledge  in  the  past  and  the  prospect 
of  an  expansion  in  the  future,  to  which  no  limits  can  be  put. 
For  the  student  of  science  sets  out  upon  his  quest  with  the 
intention  not  of  knowing  only,  but  of  understanding  what 
he  knows.  He  is  not  content  with  describing  the  form  of 
an  animal,  the  appearances  presented  during  and  after  a 
chemical  reaction,  the  sequence  of  events  which  together 
make  up  a  physiological  process  ;  but  he  asks  himself,  Why 
this  form  and  no  other?  What  is  the  cause  of  the  changes 
in  this  mixture?  To  what  need  of  the  organism  does  this 
physiological  process  respond,  and  by  what  agents  is  it 
brought  about  ?  The  questions  ' '  What  ? ' '  and  ' '  How  ? ' ' 
always  lead  up  to  the  question  "  Why  ?  "  Science  is  learning 


FIRST    PRINCIPLES  3 

with  understanding.  The  attempt  to  define  its  scope  is 
likely  to  result  in  confining  it. 

Although  all  intelligent  knowledge  is  science,  the  term 
as  commonly  used  has  certain  limitations.  It  is  especially 
applied  to  the  observation  of  natural  phenomena  and  to  the 
discovery  of  the  laws  which  govern  them,  and  hence  it 
has  come  to  be  almost  synonymous  with  inductive  science. 
Pure  speculation,  if  such  a  process  be  possible,  belongs  to 
the  province  of  philosophy,  which  province  also  includes  the 
deductions  which  result  from  the  analysis  of  consciousness. 
In  some  usages  we  find  the  term  ''science"  limited  to  the 
natural  sciences;  as,  for  example,  when  we  speak  of  "  a  man 
of  science. ' '  Yet,  on  the  other  hand,  when  the  methods  of 
science  are  employed  in  the  elucidation  of  work  which  is 
strictly  Man's  and  not  Nature's,  the  use  of  the  methods  leads 
to  the  appropriation  of  the  name.  No  one,  for  example, 
can  assert  of  any  event  recorded  in  history  that  it  is  a  fact, 
in  the  same  sense  in  which  a  biologist  is  justified  in  describ- 
ing a  particular  stage  through  which  an  egg  passes  in  the 
development  of  a  chick,  as  a  fact  ;  yet  the  work  of  an 
historian  is  said  to  be  scientific  when,  wishing  to  supply  an 
event  which  was  not  recorded  by  the  chroniclers  of  the  time 
in  which  it  presumably  occurred,  he  adopts  the  same  induc- 
tive method  which  a  biologist  would  follow  if  he  wished  to 
figure  to  himself  a  stage  in  development  which  for  any 
reason  it  is  impossible  for  him  to  observe.  On  the  same 
grounds,  we  speak  of  the  science  of  criticism  and  of  various 
other  subjects  far  removed  from  the  study  of  Nature. 

Reduced  to  its  lowest  terms,  science  is  the  observation  of 
phenomena  and  the  colligation  of  the  results  of  observation 
into  groups.  By  observation  we  discover  that  a  particular 
fish  is  coloured  like  the  seaweeds  which  grow  on  the  rocks 
in  the  neighbourhood  where  it  is  found,  and  where  we  further 
observe  it  to  be  feeding.  In  other  places  where  the  growth 
upon  the  rocks  is  differently  coloured,  we  observe  that  the 
fish  are  differently  coloured,  but  that  they  still  resemble  the 


4  AN   INTRODUCTION    TO    SCIENCE 

seaweeds.  From  many  similar  observations  giving  the  same 
result,  we  formulate  the  ' '  law' '  that  fish  which  feed  in  the 
neighbourhood  of  rocks  are  coloured  like  the  rocks  and 
the  growth  by  which  the  rocks  are  covered.  Asking  the 
question  ' '  Why  ? ' '  we  are  led  to  make  an  observation  upon 
our  own  powers  of  sight,  from  which  we  discover  that  the 
resemblance  in  colour  causes  the  fish  to  be  less  easily  visible. 
Further,  we  observe  that  many  other  animals  are  coloured 
like  their  surroundings,  and  from  these  colligated  observations 
we  draw  the  conclusion  that  animals  are  coloured  like  their 
surroundings  in  order  that  they  may  escape  notice.  Again 
the  question  ' '  Why  ?  "  is  asked.  Whose  notice  do  the  fishes 
need  to  escape?  We  can  think  of  only  two  alternatives. 
It  may  be  an  advantage  to  the  fish  not  to  be  seen  by  its  prey, 
or  it  may  be  an  advantage  to  it  to  be  invisible  to  its  enemies. 
Additional  observations  with  regard  to  protective  colouring 
have  to  be  made.  It  is  found  that  a  tiger  marked  by  trans- 
verse bars  is  less  easily  seen  against  a  background  of  tall 
grass  and  bamboos  than  an  animal  uniformly  coloured 
would  be,  or  that  the  spots  on  a  leopard  make  it  less  visible 
beneath  the  trees  through  which  the  sun  is  shining.  These 
animals  are  practically  superior  to  all  enemies.  They  do  not 
need  to  be  rendered  invisible  to  save  them  from  their  pur- 
suers, but  to  hide  them  from  the  creatures  they  pursue.  Is 
the  same  true  of  the  fish  ?  On  the  contrary,  it  is  found  that 
rock-feeding  fish  are  preyed  upon  by  many  larger  and  more 
active  kinds  ;  and,  further,  a  study  of  their  food  shows  that 
the  small  shellfish  and  worms  which  compose  it  could  not 
escape,  were  their  tyrants  never  so  conspicuous,  and  conse- 
quently the  theory  is  propounded  that  the  fish  which  feed 
near  rocks  are  coloured  like  their  surroundings  in  order  that 
they  may  escape  the  notice  of  their  enemies. 

In  all  scientific  investigations  the  same  method  is  followed 
—  observation,  colligation,  induction  —  and  as  soon  as  the 
stage  of  hypothesis  is  reached  the  process  begins  over  again. 
Fresh  observations  are  made  with  a  view  to  determining 


FIRST    PRINCIPLES  5 

whether  the  hypothesis  will  meet  all  cases.  It  is  amplified 
to  make  it  include  allied  phenomena,  or  modified  to  prevent 
it  from  excluding  them.  Perhaps  it  is  rejected  and  re- 
placed by  an  entirely  different  theory,  because  it  cannot  be 
made  to  include  phenomena  which  are  evidently  of  the  same 
order  as  those  for  which  in  the  first  instance  it  seemed  to 
assign  the  cause. 

It  is  easier  to  give  expression  to  the  general  conception 
of  science,  as  distinguished  from  knowledge,  in  metaphor 
than  in  a  reasoned  definition,  and  many  comparisons  which 
illustrate  this  welding  together  of  facts  with  thought  will 
occur  to  everyone's  mind.  Knowledge  is  a  pile  of  bricks, 
science  is  masonry.  Knowledge  is  a  shower  of  separate 
raindrops,  science  the  mountain  torrent  to  which  they  give 
birth  ;  the  forceful  stream  which  carves  canons  in  the  rock, 
traces  a  green  band  on  the  map,  turns  water-mills,  fills  the 
reservoirs  of  dusty,  dirty  towns.  Knowledge  is  discrete, 
incoordinate,  unsatisfying ;  science  is  concrete,  coordinate, 
effective.  With  observation  as  the  starting  point,  the  mind 
amasses  knowledge,  and  knowledge,  by  provoking  thought, 
leads  to  the  acquisition  of  fresh  knowledge,  out  of  which  a 
wider  thoughtfulness  builds  a  scientific  system. 

The  Aim  of  Science  is  to  know  Nature.  As  a  mer- 
chant takes  stock  of  his  goods  before  he  makes  plans  for 
placing  them  on  the  market,  so  the  student  of  science  must 
make  himself  acquainted  with  the  phenomena  which  Nature 
exhibits,  in  the  province  which  he  has  pledged  himself  to 
explore,  before  he  attempts  to  assign  to  them  their  several 
uses.  There  is  no  fact,  no  detail  of  measurement,  of  con- 
firmation, of  colour,  scent,  taste  or  distinctive  marking  which 
he  dare  overlook  as  too  trivial  for  notice,  however  trivial  may 
be  the  use  which  at  the  time  he  can  make  of  his  observation. 
All  facts  are  great  facts.  Every  observation  which  adds  a 
fact  to  the  sum  of  human  knowledge  is  a  great  discovery. 
So,  too,  is  every  conclusion  regarding  the  way  in  which  non- 
living things  react  upon  one  another,  or  living  things  perform 


6  AN   INTRODUCTION   TO    SCIENCE 

their  functions,  whether  the  induction  result  from  passive 
observation  or  from  experiment  —  from  observation  of  phe- 
nomena under  conditions  which  Nature  has  arranged,  or 
from  observations  made  under  conditions  —  arranged  by  the 
experimenter's  art.  Science  asks  first,  "What  is  it?"  next, 
"How  does  it  act?"  then,  "Why  does  it  act  in  this  way 
rather  than  in  some  other  way?"  And,  be  it  understood, 
this  question  "Why?"  is  asked  with  a  view  to  eliciting  as 
answer  either  that  certain  forces  determine  a  change  in  the 
molecular  constitution  of  the  substance,  or  that  the  action 
serves  the  organism  in  such  or  such  a  wray.  Science  never 
seeks  to  determine  the  relative  value  of  phenomena  in  the 
scheme  of  the  universe — in  the  Cosmos,  as  our  intelligence 
figures  it.  Still  less  does  science  venture  to  suppose  that 
she  can  throw  light  into  the  world  above  the  world,  the  All- 
intelligent,  of  which  our  intelligence  is  but  a  dependence. 
The  expression  "The  contest  between  Religion  and  Sci- 
ence" is  an  absurdity;  there  can  be  no  contest  in  which 
one  of  the  combatants  is  absolutely  passive.  With  the 
struggle  between  what  is  true  and  what  false  in  the  expres- 
sion of  religion,  in  dogmatic  theology,  science  has  no  con- 
cern ;  but  this  is  a  subject  upon  which  we  shall  have  a  few 
words  to  add  later  on. 

The  aim  of  science  is  to  know  Nature,  and  to  know  for 
the  sake  of  knowing.  As  has  often  been  said  of  art,  that  it 
ceases  to  be  art  as  soon  as  it  is  conscious  of  a  moral  pur- 
pose, so  may  it  be  said  of  science  that  when  the  student  sets 
before  himself  a  utilitarian  object  he  runs  the  risk  of  preju- 
dicing his  conclusions.  It  is,  of  course,  only  in  a  limited 
sense  that  this  is  true.  Great  advances  have  been  made 
by  investigators  whose  object  was  wholly  technical.  Yet, 
if  the  history  of  science  were  written,  it  would  be  found  that 
the  first  step  in  advance,  the  germ  of  the  discover}'  which 
developed  and  became  fruitful  in  the  hands  of  the  practical 
chemist,  the  mechanician,  the  pathologist,  was  discovered 
by  the  investigator  for  whom  science  lost  its  interest  as  soon 


FIRST   PRINCIPLES  7 

as  it  could  be  put  to  practical  use.  Who  anticipated  until 
Lister  devised  its  practical  application  that  the  septic  infec- 
tion of  wounds  inflicted  by  the  surgeon's  knife  could  be 
certainly  prevented  by  performing  the  operation  under  a 
cloud  of  water-vapour  in  which  carbolic  acid  is  supended? 
The  antiseptic  property  of  coal-tar  had  long  been  known. 
The  chemist  isolated  phenol,  which  proved  to  be  by  far 
the  strongest  germicide  of  all  the  substances  which  coal- 
tar  contains.  Lister  devised  a  method  for  investing  cut 
surfaces  with  an  atmosphere  of  phenol  in  which  it  is  im- 
possible for  germs  to  live.  How  far  was  Rontgen,  when 
he  discovered  —  by  accident,  truly,  rather  than  by  design — 
that  cathodic  rays  will  penetrate  organic  substances,  from 
foreseeing  that  he  was  equipping  the  surgeon  with  the  means 
of  detecting  a  bullet  hidden  in  the  flesh?  We  have  taken 
our  examples  from  that  department  of  science  of  which  the 
applications  are  of  the  greatest  use  to  mankind,  but  similar 
illustrations  are  afforded  by  every  subject  of  obvious  prac- 
tical utility.  The  discovery  is  made  by  the  investigator  who 
works  without  weighing  the  question  of  whether  his  line  of 
research  is  more  likely  to  benefit  mankind  than  any  other 
line.  The  practical  man  who  is  on  the  watch  for  sugges- 
tions seizes  the  discovery  and  applies  it  to  the  uses  of  his 
profession. 

The  superiority  of  pure  science  to  applied  science  as  a 
field  for  research  is  even  more  easily  proved  from  the  op- 
posite side.  Every  investigator  who  works  in  a  technical 
laboratory  knows  the  difficulty  of  following  a  useful  line  of 
research.  He  is  constantly  thrown  back  upon  himself  with 
the  conviction  that  only  by  some  happy  accident  will  he 
discover  the  solution  to  the  problem  ;  while  at  almost  every 
turn  in  his  investigations  he  starts  questions  to  which  he 
is  astonished  to  find  that  no  answer  has  yet  been  given, 
problems  which  tempt  him  to  forget  the  purpose  with  which 
he  set  out,  to  leave  the  main  road  and  to  follow  the  by- 
path, not  because  he  believes  that  it  will  lead  him  to  a 


8  AN   INTRODUCTION   TO   SCIENCE 

source  of  food  or  fame,  but  simply  prompted  by  curiosity 
to  find  out  whither  it  leads.  It  may  be  a  pathologist  who 
sets  out  to  search  for  an  antitoxin.  He  has  no  interest,  of 
which  he  is  conscious,  in  the  chemistry  of  complex  nitrog- 
enous compounds.  He  will  apply  to  the  professed  chemist 
for  all  the  information  he  requires.  But  when  his  questions 
regarding  the  nature  of  the  albuminoid  constituents  of  serum 
are  not  satisfactorily  answered,  he  finds  himself  involved  in 
a  long  research,  which  soon  becomes  an  end  in  itself,  and 
not  merely  a  means  to  an  end.  A  hundred  similar  illus- 
trations might  be  given.  But  few  scientific  workers  are  still 
engaged  in  middle  life  upon  the  researches  which  they  once 
thought  the  main  objects  of  their  existence.  "The  thoughts 
of  youth  are  long,  long  thoughts  ! "  At  sunrise  the  distant 
peaks  are  clear,  while  the  barriers  which  break  the  road 
that  must  be  traversed  before  their  slopes  are  reached  are 
hid  in  mist.  At  noonday  the  pass  which  has  yet  to  be 
crossed  before  a  camping-place  is  reached  occupies  a  larger 
place  in  the  traveller's  thoughts  than  the  loftiest  of  the 
mountains  which  lie  beyond. 

It  may  almost  be  said  that  science  owes  its  progress  to 
the  deserters  from  the  professions.  A  lad  starts,  as  he  is 
bound  to  do,  to  qualify  as  a  manufacturing  chemist,  an 
engineer,  a  doctor.  He  discovers  in  himself  an  aptitude 
for  one  or  other  of  the  sciences  upon  which  his  profession 
is  based,  and  he  stays  behind  to  work  at  the  subject  which 
interests  him  most,  perhaps  for  a  short  time  before  pressing 
on  towards  his  professional  career,  perhaps  for  life.  It  is 
for  this  reason  that  a  school  of  pure  science  is  strong  only 
when  it  gives  opportunities  of  passing  on  to  professional 
work.  The  remarkable  success  of  the  scientific  schools  at 
Cambridge  in  recent  years  is  largely,  if  not  chiefly,  due  to 
the  growth  of  the  medical  school.  Every  laboratory  now 
has  its  complement  of  graduates  who,  while  they  may  act 
as  lecturers  or  demonstrators,  give  up  the  greater  part  of 
their  time  to  research.  Probably  two  out  of  every  three 


FIRST    PRINCIPLES  9 

of  these  men  entered  the  University  as  medical  students. 
But  some  found  physics  or  chemistry,  others  botany  or 
zoology,  others  physiology,  anatomy,  or  pathology,  of  such 
surpassing  interest  that  they  abandoned  all  intention  of 
practising  medicine  in  order  that  they  might  give  their  lives 
to  science.  The  growth  of  the  engineering  school  is  lead- 
ing to  a  like  result.  And  one  cannot  but  regard  the  gain 
to  pure  science  as  far  outweighing  the  loss  to  applied 
science.  Pure  science  cannot  hope  for  numerous  recruits. 
Its  prizes  are  few,  its  disappointments  many,  even  for  those 
who  show  a  special  aptitude  for  its  pursuit.  The  advice 
which  we  always  give  to  a  lad  who  desires  to  devote  him- 
self to  science  is,  "Prepare  yourself  for  a  profession  in 
which  your  favourite  science  plays  an  important  part,  and 
trust  that  if  you  have  the  capacity  for  the  science  you  will 
secure  the  opportunity  of  pursuing  it. ' '  Many  a  Cambridge 
graduate  is  now  grateful  to  his  teachers  for  urging  him  to 
persevere  in  obtaining  a  medical  degree  at  a  time  when 
he  wished  to  throw  up  every  other  prospect  for  the  sake 
of  one  or  other  of  the  sciences  upon  which  medicine  rests. 
After  taking  the  degree,  he  has  returned  to  science  to  find 
that  after  all  it  would  not  provide  him  with  a  livelihood,  or 
that  his  capacity  for  research  was  less  than  he  had  assumed, 
and  therefore  he  has  again  given  himself  heartily  to  the  pro- 
fession from  which  for  a  time  he  thought  himself  seduced. 

The  aim  of  science  is  to  know  Nature,  and  the  student 
can  obtain  an  intimate  knowledge  of  his  science  only  by 
watching  Nature's  every  manifestation.  It  is  impossible  to 
know  her  through  report.  It  might  be  supposed  that  a  man 
could  become  a  learned  chemist  without  entering  a  labora- 
tory, but  it  is  not  so.  There  is  in  the  writings  of  those 
who  compile  text-books,  without  putting  the  statements 
which  they  copy  from  other  authors  to  the  test  of  experi- 
ence, a  want  of  accuracy  and  proportion  which  give  a  false 
ring  to  the  work.  Everyone  who  has  travelled  knows  that 
the  thing  as  he  saw  it  never  exactly  corresponded  to  the 


io  AN    INTRODUCTION   TO    SCIENCE 

mental  picture  which  written  descriptions  had  caused  him 
to  draw.  No  one  can  convey  in  words  to  his  hearer  or 
reader  an  accurate  conception  of  any  phenomenon,  even 
though  he  may  have  observed  it  himself,  and  the  passing 
of  the  description  through  a  second  mind  throws  the  picture 
still  further  out  of  focus.  But  it  is  not  only  in  accuracy  that 
the  mental  picture  based  upon  descriptions  is  inferior  to 
the  picture  formed  from  autoptic  observation,  but  also  in 
proportion.  All  facts  are  equally  true,  and  yet  every  in- 
vestigator knows  that  certain  things  which  he  observes 
influence  his  judgment  more  than  others,  so  that  when  he 
is  formulating  a  hypothesis  he  takes  care  that  it  squares 
with  them.  This  perfect  assurance  of  the  indisputable 
accuracy  of  one's  observations  is  a  sentiment  difficult  to 
convey,  and  since  in  the  higher  branches  of  all  subjects  it 
is  necessary  to  trust  to  the  repute  of  observers  in  various 
special  fields,  it  is  of  the  greatest  consequence  that  every 
one  who  assumes  the  position  of  teacher  should  have  had 
such  personal  Experience  of  research  as  will  enable  him  to 
adjust  the  amount  of  credence  which  he  gives  to  the  reports 
of  other  workers.  The  supreme  value  of  first-hand  knowl- 
edge has  been  so  much  insisted  upon  of  late  years  that 
it  seems  hardly  necessary  to  accentuate  it,  yet  the  clearest 
definition  of  the  aim  of  science  is  that  it  seeks  to  know 
Nature  by  personal  contact. 

From  a  personal  intimacy  with  Nature  results  such  a 
quick  understanding  of  her  manifestations  as  to  constitute 
what  in  other  spheres  of  thought  would  be  termed  intuition. 
The  process  of  induction  from  observations  occurs  so  quickly 
that  the  observer  draws  his  conclusions  as  soon  as  he  sees 
the  phenomena,  and  he  is  therefore  able  to  foretell  with  an 
accuracy  which  his  ability  to  give  the  reasons  for  his  opinion 
would  not  justify  what  will  happen  next — what  will  be  the 
result  of  certain  novel  combinations.  Shall  we  call  this 
scientific  imagination?  The  term  is  self-contradictory,  yet 
its  use  is  in  some  degree  justified  by-  the  analog)'  of  art. 


FIRST    PRINCIPLES  n 

Let  it  stand  as  a  metaphor.  To  the  man  whose  knowledge 
is  partial  and  second-hand,  the  ease  with  which  a  specialist 
who  has  the  personal  and  intimate  knowledge  of  his  subject 
which  we  describe  can  give  the  correct  explanation  of  a 
phenomenon  which  he  observes  for  the  first  time,  or  can 
judge  between  discrepant  reports  of  observations,  seems 
to  be  too  rapid  for  reason  ;  and  the  specialist  himself  finds, 
when  he  attempts  to  give  his  reasons,  that  they  hardly 
justify  the  strength  of  his  conviction. 

Perhaps  it  is  permissible  to  use  the  expression  "scientific 
imagination"  in  a  still  larger  sense.  In  the  army  of  workers 
who  are  advancing  the  boundary  of  knowledge  there  are 
some  who  gain  for  it  a  furlong,  while  others  move  it  forward 
but  an  inch.  And  those  who  make  the  greatest  advance 
do  so  because  they  bring  to  bear  upon  their  subject  the 
same  mental  qualities  which  constitute  imagination  in  an 
artist.  The  artist  imagines  new  combinations  of  form, 
colour,  musical  notes.  The  man  of  science  imagines  new 
combinations  of  force,  new  conditions  of  action.  Some  men 
are  incapable  of  picturing  anything  outside  the  limits  of 
their  experience  —  others  can  devise  new  conditions,  and 
can  foretell  what  would  happen  to  inorganic  matter  or  to 
a  living  thing  if  placed  in  circumstances  which,  so  far  as 
they  know,  have  never  concurred  before.  The  develop- 
ment of  an  acquaintance  with  Nature  so  sympathetic  and 
confidential  as  to  allow  the  worker  to  share  her  secrets, 
and  to  unite  with  her  in  designing  new  combinations,  is 
the  highest  result  of  scientific  training. 

The  Boundaries  of  Science.— Science  extends  no 
further  than  knowledge.  Its  agents — the  five  senses — collect 
stores  of  facts  upon  which  science  lives  and  grows.  It  has 
no  traffic  with  the  unknowable  ;  nor  can  it  cross  the  border- 
line which  separates  the  world  of  the  senses  from  the  world 
of  consciousness,  or  barter  its  facts,  gathered  from  the 
external  universe,  for  the  equally  real  facts  which  the  in- 
dividual learns  by  self-examination. 


12  AN   INTRODUCTION   TO    SCIENCE 

And  not  only  is  science  limited  to  the  world  of  sense,  but 
even  this  world  expands  into  a  nebulous  zone  of  half-science 
before  the  unknowable  is  reached.  There  is  a  limit  beyond 
which  scientific  thought  cannot  penetrate ;  not  because  the 
outer  realm  does  not  appertain  to  science,  but  because 
experience  which  bears  up  thought  with  varying  degrees  of 
firmness — just  as  matter  in  its  several  conditions  of  aggrega- 
tion, solid,  liquid,  gaseous,  supports  animals  which  stand, 
swim,  fly — becomes  too  rarified  a  medium  for  human  in- 
telligence to  mount  in. 

Much  painful  mental  effort  may  be  saved  by  the  honest 
recognition  of  the  limitations  of  science.  A  child,  at  the 
age  when  errant  curiosity  compels  it  to  ask  questions,  and 
the  simplicity  of  childhood  believes  that  every  question  has 
an  answer,  lies  awake  at  night,  beating  its  brains,  in  the 
struggle  to  understand  what  happened  before  time  began, 
what  space  is  like  beyond  the  outside  of  infinity,  and 
whether,  if  there  be  no  outside  to  space,  the  comet,  which 
travels  fifty  miles  a  second  for  a  century',  is  not  in  the  same 
place  all  the  time.  An  astronomer  is  compelled  to  use  the 
terms  Time,  Space,  Movement ;  yet  he  is  as  little  able  as  a 
child  to  form  a  mental  picture  of  the  absolute  meaning  of  the 
words.  He  uses  them  so  often,  and  they  serve  his  purpose 
when  explaining  the  sidereal  system  so  well,  that  he  forgets 
the  date  at  which  he  abandoned  the  attempt  to  realise  Time, 
Space  and  Movement  as  absolute — what?  things  or  the 
attributes  of  things  ? — and  settled  down  to  speaking  of  them 
henceforward  as  relations. 

The  first  step  in  chemistry  or  physics  demands  the  recog- 
nition of  a  distinction  between  Matter  and  Force.  But  what 
is  matter,  and  what  force  ?  Matter  is  that  upon  which  force 
acts  ;  force  is  that  which  acts  upon  matter.  Yet  it  is  late,  if 
ever,  that  the  physicist  or  chemist  ceases  his  endeavour  to 
form  a  nearer  conception  of  the  meaning  of  that  which  in  its 
manifestations  is  the  subject  of  his  life-work.  Time  after 
time  he  traces  the  chain  of  inductions  back,  and  still  further 


FIRST    PRINCIPLES  13 

back,  to  find  himself  before  the  weary  paradox  :  that  ultimate 
matter  is  force,  and  ultimate  force  is  matter.  The  definite 
proportions  in  which  "elements"  combine  together  leaves 
the  chemist  in  no  doubt  as  to  the  ultimate  constitution  of 
matter.  It  consists  of  atoms  ideally  indivisible,  because  we 
can  conceive  of  nothing  which  can  divide  them — although 
both  physicist  and  chemist  are  beginning  to  regard  the 
' '  atom ' '  of  Walton  as  a  cluster  of  atoms,  or  sub-atoms  of 
matter,  more  fundamental  than  the  elements  ;  similar  atoms 
unite  into  squads  or  molecules  which  are  units  of  chemical 
combination.  A  binary  compound  is  a  combination  of  x 
molecules  of  one  element  with  y  molecules  of  another.  The 
simple  numerical  relations  between  the  various  elements  as 
regards  their  atomic  weight  and  specific  heat,  which  enables 
the  chemist  to  arrange  them  into  several  parallel  series 
according  to  the  "periodic  law,"  leads  him  to  the  conclusion 
that  there  is  only  one  kind  of  true  atom  variously  united 
into  groups  by  cohesive  force.  If  there  is  only  one  ultimate 
indivisible  atom,  there  must  be  as  many  kinds  of  cohesive 
force  as  there  are  different  "elements."  "Impossible," 
the  physicist  exclaims  ;  ' '  there  is  only  one  kind  of  cohesive 
force.  Either  there  are  as  many  kinds  of  atoms  as  there  are 
elements,  or  else,  as  is  more  probable,  your  atom  is  not 
matter  at  all,  but  a  centre  of  force — for  force  is  the  one 
thing  which  you  cannot  think  away,  and  the  difference 
between  one  element  and  another  lies  in  the  amount  of  force 
which  each  centre,  or  atom,  represents."  The  simplicity  of 
the  positions  taken  up  by  the  most  profound  thinkers, 
when,  after  passing  through  abstruse  and  recondite  pro- 
cesses of  reasoning,  they  try  to  take  a  steady  view  of  the 
ultimate  constitution  of  things,  would  bring  a  smile  to 
the  face  of  a  Greek  philosopher  accustomed  to  more 
generous  theories.  The  most  learned  physicist  becomes 
as  a  little  child. 

The  biologist  at  an  early  stage  in  his  career  begins  to 
ask  himself,  What  is  life?    As  age  advances  he  finds  that 


14  AN   INTRODUCTION    TO    SCIENCE 

although  he  has  learnt  something  of  the  ways  in  which  life 
manifests  itself,  and  can  formulate  an  excellent  definition  of 
the  means  by  which  life  maintains  itself,  he  is  farther  off 
than  ever  from  finding  a  form  of  words  which  will  define 
what  life  is. 

The  psychologist,  beginning  with  the  study  of  the  structure 
of  the  nervous  system,  passes  on  to  the  consideration  of  its 
modes  of  action,  modifies  the  conditions  under  which  it  acts 
in  every  way  which  his  ingenuity  can  devise,  and  patiently 
measures  every  measurable  reaction-time  ;  yet  at  the  end  of 
his  work  he  exclaims,  "But  this  is  only  reflex  action.  It 
was  consciousness  that  I  set  out  to  investigate.  All  the 
researches  which  I  have  been  carrying  out  serve  merely  to 
throw  light  upon  the  physiology  of  the  nervous  system. 
They  teach  me  nothing  about  the  working  of  the  mind. 
Truly  I  have  found  out  a  good  deal  about  the  apparatus 
which  the  mind  employs,  but  I  know  as  little  about  the  mind 
itself  as  when  I  started."  And  when  his  four-year-old 
daughter,  kissing  him  good-night,  asks,  "Daddy,  where  do 
I  go  to  when  I  go  to  sleep  ?  Do  I  go  away  from  myself  and 
come  back  again  in  the  morning?"  he  answers  humbly,  "I 
do  not  know." 

The  candid  recognition  of  the  limitations  of  science  can 
do  no  harm.  Even  within  the  proper  sphere  of  science  there 
is  a  level  beyond  which  thought  finds  no  foothold  in  experi- 
ence, and  there  is  another  sphere,  the  sphere  of  conscious- 
ness, or  the  world  of  spirit — in  the  sense  in  which  St.  Paul 
uses  the  term  spirit,  the  "  active  reason  "  or  intelligent  soul 
of  Aristotle — for  which  science  has  no  passport.  The 
methods  of  science  may  be  used  in  investigating  the  phe- 
nomena of  consciousness,  but  the  use  of  her  methods  does 
not  entitle  science  to  claim  the  results.  Even  the  use  of 
scientific  terms  in  describing  spiritual  phenomena  introduces 
a  grave  risk  of  misunderstanding.  Consciousness  cannot 
perceive  things  outside  itself.  The  phenomena  of  which  it 
takes  cognizance  are  its  own  varying  states  of  exaltation  and 


FIRST   PRINCIPLES  15 

depression,  activity  and  relaxation.  We  cannot  measure 
love  or  hate,  or  duty  in  calories,  or  foot-pounds,  or  amperes, 
or  any  other  units,  and  when  we  enter  the  realm  in  which 
emotions  hold  sway  we  have  to  leave  our  science  behind. 
Perhaps  this  is  the  mistake  which  certain  French  psychol- 
ogists, who  look  upon  man,  body  and  mind,  as  merely  the 
product  of  his  environment,  have  made.  They  regard  him 
as  a  machine  which  responds  in  a  rational  way  to  every 
impinging  force,  whereas  experience  tells  us  that  even  the 
sterner  sex  seldom  transmits  the  stimuli  a-(-4+6  as  an  action 
equal  to  12.  An  emotional  bias  almost  always  prevents  us 
from  working  out  the  sum  aright.  No  two  persons  obtain 
exactly  the  same  result. 

Science  cannot  penetrate  into  the  world  of  consciousness. 
The  writer  of  "  Natural  Law  in  the  Spiritual  World  "  showed 
a  singular  misconception  of  the  meaning  of  the  word  law,  as 
well  as  an  inability  to  interpret  either  nature  or  spirit. 

" There  is,"  he  said,  "a  sense  of  solidity  about  a  Law  of 
Nature  which  belongs  to  nothing  else  in  the  world. ' '  But  a 
law  is  nothing  more  than  a  docket  into  which  we  collect 
phenomena  which  have  something  in  common.  When  it  is 
discovered  that  certain  facts  are  not  isolated,  but  that  they 
are  similar  to  certain  other  facts,  they  are  united  into  a  group 
which  is  held  together  by  the  character  which  they  possess 
in  common,  and  the  statement  that  they  all  possess  this 
character  is  enunciated  as  a  "law."  Early  man  discovered 
the  law  that  stones  fall  to  the  ground  ;  later  it  was  discovered 
that  water  "seeks  its  own  level ; "  that  a  heavy  body  when 
immersed  in  fluid  displaces  a  bulk  of  fluid  equal  to  its  own 
bulk  ;  that  the  moon  remains  at  a  fixed  distance  from  the 
earth.  All  these  apparently  diverse  phenomena  fall  into  a 
group.  We  therefore  tie  them  up  with  the  same  tape  and 
put  them  into  a  docket  labelled  "law  of  gravitation."  If 
asked  for  a  definition  of  the  Law  of  Gravitation,  we  state 
that  "Gravity  is  a  universal  property  of  matter,  in  virtue  of 
which  every  body  gravitates  to  every  other  body ;  and  the 


16  AN   INTRODUCTION   TO    SCIENCE 

gravitations  are  proportional  to  the  quantity  of  matter  in 
that  other  body,  and  inversely  proportional  to  the  square  of 
the  distance  from  it."  But  this  is  not  an  explanation  of  the 
nature  of  gravitation,  still  less  is  it  an  explanation  of  its 
cause.  It  is  merely  the  collection  of  like  phenomena  into  a 
single  group.  As  knowledge  progresses  other  phenomena 
will  be  seen  to  illustrate  the  law  of  gravitation,  or  will 
demand  inclusion  with  those  phenomena  which  \ve  have 
already  enumerated  in  a  common  law.  Hydrogen  gas,  when 
liberated  into  the  atmosphere,  is  not  attracted  by  the  mass  of 
the  earth  ;  on  the  contrary,  it  escapes  from  our  atmosphere 
and  flies  off  into  space.  But  this  does  not  invalidate  the 
law  of  gravitation.  The  falling  of  a  stone  to  the  earth  and 
the  flying  away  from  the  earth  of  hydrogen  gas  must  be 
ultimately  due  to  a  common  cause.  It  is  conceivable  that 
some  day  the  "law  of  gravitation"  will  be  enlarged  until 
its  formula  includes  these  apparently  opposite  phenomena, 
in  which  case  it  is  not  unlikely  that  scientific  writers  will 
find  that  the  law  in  its  new  form  is  too  wide  for  useful  appli- 
cation. The  phenomena  which  it  comprises  will  be  seen  to 
fall  into  two  or  more  groups,  the  members  of  each  of  which 
have  more  in  common  with  one  another  than  they  have  with 
those  in  the  other  groups.  New  proximate  laws  will  then  be 
formulated  within  the  law  of  gravitation.  The  docket  "  law 
of  gravitation"  will  be  subdivided,  and  the  new  dockets  will 
include  a  greater  number  of  phenomena  than  the  "  law  "  as 
now  formulated  can  be  made  to  do. 

Not  only  did  the  writer  of  "  Natural  Law  in  the  Spiritual 
World"  mistake  the  meaning  and  value  of  law,  but  he  was 
curiously  obtuse  to  the  trend  of  his  own  arguments.  He 
found  that  an  investigation  of  the  spiritual  world,  as  Chris- 
tians understand  it,  shows  that  its  "laws"  are  similar  to 
those  which  man  has  formulated  for  the'  phenomena  of 
nature.  Mr.  Drummond  found  that  in  the  supernatural  world 
as  revealed  in  the  Bible,  the  laws  with  which  we  are  familiar 
in  the  physical  world  hold  sway.  Had  he  found  other  laws 


FIRST    PRINCIPLES  17 

— laws  which  have  no  counterpart  in  nature — he  would  have 
discovered  a  new  line  of  evidence  of  the  existence  of  the 
spiritual  world.  This  new  world,  with  its  own  laws,  would 
be  clearly  an  independent,  self-sufficient  world,  and  not 
merely,  as  sceptics  assert  it  to  be,  a  reflection  of  the  physical 
world — the  projection  of  man's  experience.  "But,"  says 
Mr.  Drummond,  ' '  what  is  required  to  draw  Science  and 
Religion  together  again — for  they  began  the  centuries  hand 
in  hand — is  the  disclosure  of  the  naturalness  of  the  super- 
natural." "The  position  we  have  been  led  to  take  up  is 
not  that  the  Spiritual  Laws  are  analogous  to  the  Natural 
Laws,  but  that  they  are  the  same  Laws.  It  is  not  a  question 
of  analogy  but  of  Identity.  The  Laws  of  the  invisible  are 
the  same  Laws,  projections  of  the  natural,  not  the  super- 
natural. ' ' 

"God  made  man  in  his  own  image,"  says  the  Bible. 
"Man  made  God  in  his  own  image,"  answers  Comte. 
Clearly,  there  is  no  third  alternative.  Either  our  religion  is 
based  upon  a  revelation  of  God,  or  it  is  our  own  invention. 
Nevertheless,  it  may  be  that  both  statements  are  true.  God 
made  Man  in  His  own  image,  and  implanted  in  him  the 
instinct  for  feeling  after  Himself.  Ever  since  Man  became  a 
rational  being  he  has  been  trying  to  picture  God.  But  still 
the  truest  picture  is  the  one  which  carries,  most  meaning  to 
the  individual,  whether  he  approaches  it  with  ceremony  and 
veiling  its  glory  with  a  cloud  of  incense,  or  feels  the  familiar 
Presence  by  his  own  fireside.  The  analogies  between  the 
world  of  nature  and  the  world  of  religion  pointed  out  by 
Mr.  Drummond  prove,  if  they  prove  anything,  that  much 
that  Christians  regard  as  a  revelation  is  the  product  of  imagi- 
nation. Fortunately  neither  unwise  friends  of  religion  nor 
its  overt  enemies  can  prove  that  there  is  no  supernatural 
world ;  but  the  book  which  we  have  referred  to  has  done 
more  than  much  hostile  criticism  in  the  direction  of  proving 
the  anthropomorphy  of  the  religion  of  the  Bible.  It  demon- 
strates the  intercalation  of  the  fruits  of  human  experience 


i8  AN   INTRODUCTION    TO   SCIENCE 

into  the  expression  of  religion.  Pointing  to  the  tool  marks, 
Mr.  Drummond  shows  that  our  model  of  the  temple  was  not 
made  without  hands. 

"The  antagonism  between  religion  and  science"  is  an 
absurd  expression  which  was  used  most  frequently  after  the 
publication  of  the  "Origin  of  Species."  Religious  men  of 
the  last  generation  believed  every  statement  in  the  Bible  to 
be  a  statement  of  fact.  Science  proved  that  the  earth  did 
not  come  into  existence  in  the  stages  described  in  the  first 
book  of  Genesis ;  that  the  various  species  of  animals  and 
plants  were  not  separate  creations,  that  every-  organ  in  man's 
body  shows  that  it  has  been  adapted  by  a  process  of  evolu- 
tion from  an  organ  of  the  body  of  an  animal  belonging  to 
the  "  brute  creation."  Men  who  clung  to  the  literal  interpre- 
tation of  the  Bible  as  essential  to  the  Christian  faith  fought 
against  the  truths  of  science.  They  preferred  to  disbelieve 
the  conclusions  to  which  their  judgment  came  on  the 
evidence  of  their  senses.  But  science  had  no  quarrel 
with  religion.  It  was  the  false  in  religion  quarrelling  with 
the  true. 

The  religious  man  may  be  a  man  of  science  or  he  may  be 
unlearned  and  out  of  the  way.  If  he  is  ignorant  he  sees  no 
reason  for  not  accepting  scripture  allegories  as  records 
of  facts ;  the  picture  is  to  him  a  glimpse  into  real  life.  A 
learned  man,  on  the  other  hand,  recognizes  the  pigments 
with  which  the  picture  is  painted,  and  can  trace  the  process 
by  which  the  colours  have  been  added  to  the  canvas 
throughout  successive  ages.  Yet  the  subject  of  the  picture, 
the  religious  idea  which  it  shadows  forth,  is  far  more  to  him 
than  it  is  to  the  ignorant  man,  who  gives  to  the  details  of 
outline  and  colouring  a  naturalistic  interpretation. 

It  is  with  great  reluctance  that  we  have  touched  upon  this 
subject,  yet  it  has  occupied  so  large  a  place  in  the  thought 
of  the  last  forty  years  that  it  cannot  be  passed  over  in  a 
general  survey  of  the  history  of  science.  Well-meaning 
but  inept  attempts  at  "reconciliation"  have  increased  the 


FIRST    PRINCIPLES  19 

difficulty  of  those  who  endeavor  to  be  true  to  science  and 
at  the  same  time  to  hold  fast  in  their  allegiance  to  the  Truth 
which  is  beyond  the  reach  of  science.  It  is  only  on  this 
ground  that  we  have  ventured  to  point  out  a  line  of  thought 
which,  as  we  think,  justifies  us  in  keeping  the  two  spheres 
distinct,  and  because  we  can  imagine  no  process  so  likely  to 
undermine  the  Spiritual  World  as  the  attempt  to  prove  that 
it  is  governed  by  Natural  Law.  It  is  not  within  the  prov- 
ince of  this  book  to  deal  with  spiritual  ideas  or  to  suggest 
methods  which  may  prove  constructive  in  theology ;  but 
looking  upon  the  question  from  the  standpoint  of  scientific 
philosophy,  we  have  ventured  to  point  out  the  harm  which 
may  result  from  a  misconception  of  the  meaning  of  the 
term  by  which  similarity  amongst  phenomena  is  expressed. 
"  Law  "  is  a  term  which  is  applied  to  a  sequence  or  a  group- 
ing of  phenomena  only  in  a  metaphorical  sense.  It  is  a 
convenient  term  which  men  of  science  use  in  classifying 
their  observations,  often  as  a  synonym  for  hypothesis.  They 
never  intend  to  imply  that  Nature  is  bound  by  rules  in  the 
sense  in  which  Man  is.  The  misapprehension  of  the  meta- 
phor by  persons  who  have  not  been  trained  in  science,  and 
by  some  who  have  been,  has  led  to  confusion,  but  it  is 
difficult  to  think  of  any  term  which  might  replace  it. 

The  German  equivalent  "gesetz,"  which  really  means  a 
statute,  is  still  more  open  to  objection.  During  the  last  forty 
years  a  steady  outflow  of  books  has  been  produced  by 
champions  who,  accepting  the  challenge  of  Comte  and  Hux- 
ley, have  striven  to  justify  their  faith  in  the  unseen  by  an 
appeal  to  the  seen  ;  and  since  the  word  Law  is  used  by  all 
these  writers  in  a  wholly  unjustifiable  sense,  and  since  this 
question  of  the  relation  of  religion  to  science  has  occupied 
many  earnest  minds,  we  have  thus  severely  criticised  the 
most  mistaken  and  therefore  the  most  harmful  of  all  this 
series  of  apologetics.  The  worship  of  Law  has  done  sorre 
harm  in  science.  The  introduction  of  the  word  into 
theology  is  fraught  with  graver  dangers.  It  can  but  lead  to 


20  AN  INTRODUCTION    TO    SCIENCE 

an  unworthy  conception  of  the  Deity.  An  absolute  monarch 
is  bound  by  no  statutes.  No  laws  stand  between  God  and 
the  phenomena  of  His  creation. 

Has  science  any  quarrel  with  superstition  ?  The  question 
does  not  need  an  answer.  Superstition  is  belief  not  founded 
upon  knowledge.  It  is  the  product  of  the  imagination  of  the 
individual,  suggested  and  reinforced  by  the  traditions  of  his 
still  more  ignorant  ancestors.  The  imagination  does  not 
devise  objects  which  are  contrary  to  knowledge.  Its  pro- 
ducts are  within  the  bounds  of  possibility  as  they  are  under- 
stood at  the  time.  But  as  knowledge  increases,  it  is  inevitable 
that  some  forms  of  superstition  should  be  found  to  be  con- 
trary to  this  wider  experience. 

The  educated  have  ceased  to  believe  in  elves  and  gnomes 
and  hobgoblins,  although  there  is  a  fringe  of  the  population 
living  in  out-of-the-way  places,  wrhere  nature  is  vast  and 
mysterious,  who  are  still  as  firmly  convinced  of  the  existence 
of  their  banshees  as  more  civilised  country  folk  are  of  their 
ghosts.  Few  of  us,  indeed,  are  quite  convinced  that  ghosts 
are  merely  the  products  of  the  imagination.  ' '  There  are 
more  things  in  heaven  and  earth,  Horatio,  than  are  dreamt 
of  in  your  philosophy."  It  is  a  common  and  a  reasonable 
answer  that  while  we  trust  our  senses  to  tell  us  what  is,  it  is 
useless  to  appeal  to  them  when  we  wish  for  an  assurance  that 
certain  things  are  not.  Many  a  man,  when  asked  whether  he 
believes  in  ghosts,  is  fain  to  answer  in  the  words  of  the 
cautious  Scot,  "Weel,  I  wun'na  say  that  such  things  cud'na 
be."  No  wise  man  would  assert  that  ghosts  cannot  be. 
But  a  man  trained  in  science  has  great  difficulty  in  believing 
in  the  ghost  as  it  is  always  described  to  him. 

Some  years  ago  a  much-haunted  house  in  Buckingham- 
shire was  placed  at  the  disposal  of  the  Society  for  Psychical 
Research.  No  house  could  have  afforded  a  better  oppor- 
tunity for  the  patron  of  ghosts  to  meet  one  of  his  clients. 
The  ghost  gave  the  best  of  references.  Three  clergymen 
vouched  for  it,  one  in  a  long  affidavit,  These  gentlemen  also 


FIRST    PRINCIPLES  21 

asserted  that  the  ghost  was  perfectly  punctual  and  regular  in 
its  habits.  Every  night  as  the  clock  struck  twelve  it  mounted 
the  creaking  stairs,  entered  the  haunted  room,  deposited  its 
pack  on  the  floor  (it  was  the  ghost  of  a  murdered  pedlar), 
and  uttered  its  formula — "Three  stages  more,  and  then 
comes  death  ! ' '  Several  Cambridge  men,  including  the 
writer,  spent  a  solitary  night  in  the  room  with  the  blood- 
stained floor — the  blood  was  found  on  examination  to  be 
soluble  in  benzol,  but  that  is  a  scientific  detail — yet  no  ghost 
appeared.  Not  that  the  villagers'  belief  in  their  ghost  was 
in  the  least  shaken  by  what  might  be  regarded  as  a  base 
refusal  on  its  part  to  substantiate  their  story.  They  were  not 
even  surprised  at  the  disappointment  of  the  seekers  after 
truth.  "What  was  the  use,"  they  asked,  "of  sending  men 
from  Cambridge  to  see  a  ghost?  Why,  they  don't  believe  in 
anything  in  Cambridge!"  Ghosts  only  show  themselves 
to  persons  who  are  prejudiced  in  their  favour,  and  at  the 
Universities  such  a  pre-possession  is  uncommon  it  is  to  be 
hoped.  The  credulity  implied  by  the  villagers'  word 
"believe"  is  not  a  scientific  attitude  of  mind. 

Now,  without  for  a  moment  admitting  that  a  scientific 
training  deadens  the  senses  to  sights  and  sounds  which  the 
unscientific  can  perceive,  we  assert  that  loyalty  to  science 
compels  us,  whether  we  can  or  cannot  see  and  hear  the 
ghost,  to  ask  for  an  explanation  of  its  power  of  rendering 
itself  visible  and  audible.  Emission  of  light  and  production 
of  sound  are  exhibitions  of  force,  and  by  the  law  of  the 
conservation  of  energy — a  law  which  cannot  be  called  in 
question — force  is  never  either  created  or  lost.  When  it 
appears  to  us  as  a  new  force,  we  know  that  it  is  pre-existing 
force  translated  into  a  new  form.  The  force  set  free  on  the 
combustion  of  coal  came  from  the  sun  as  radiant  heat,  which 
enabled  plants  to  decompose  carbonic  acid  into  carbon  and 
oxygen.  When  coal  is  burnt  the  carbon  and  oxygen  again 
unite,  and  the  force  which  the  plants  stored  up  is  set  free. 
Whatever  a  ghost  may  be,  it  cannot  create  force.  Further, 


22  AN   INTRODUCTION   TO    SCIENCE 

we  know  that  force  cannot  be  exhibited  except  through 
matter.  Light  is  emitted  by  a  burning  candle,  sound  by  a 
vibrating  violin  string.  Therefore  the  ghost  which  emits 
light  and  sound  must  be  material.  These  difficulties  do  not 
occur  to  the  simple  villager,  because  to  him  force  is  not 
a  reality.  It  is  an  attribute,  not  a  thing.  He  can  see  no 
difficulty  in  supposing  that  a  spirit  can  create  force. 

If  we  ask  the  more  learned  believer  in  ghosts  the  obvious 
question — Whence  comes  the  force  by  which  a  ghost  reveals 
itself?  —  he  answers  that  the  question  is  beside  the  mark. 
Every  part  of  the  body  has  its  representation  in  spirit,  and 
our  spirit  is  capable  of  perceiving  other  spirits  without  the 
intervention  of  the  senses.  ' '  No  force  passes  from  the  ghost 
to  you,"  he  assures  us.  It  is  undoubtedly  a  thinkable  posi- 
tion, so  far  as  the  body  is  concerned,  but  what  about  the 
clothes?  Do  they  acquire  a  "spirit"  by  contact  with  a 
human  being  ?  If  they  do  not,  how  is  it  that  the  clothing  of 
the  ghost  makes  itself  sensible  to  our  spirits  ?  Few  chapters 
in  social  history  are  more  interesting  than  the  evolution  of 
the  ghost.  It  has  steadily  progressed  in  the  wake — truly  a 
long  way  in  the  wake — of  science.  Who  can  tell  what  the 
unexceptionable  ghost  of  the  twentieth  century  may  be  like  ? 

Proficiency  in  science  is  shown  by  a  masterly  skill  in 
cross-examining  nature  ;  and,  as  every  lawyer  knows,  no 
case  is  proved  as  long  as  any  antagonistic  fact,  however 
trivial,  cannot  be  explained  away.  ' '  The  seeker  after  truth 
must  himself  be  truthful,  truthful  with  the  truthfulness  of 
nature.  .  .  .  Unscientific  man  is  often  content  with  the 
'  nearly '  and  the  '  almost. '  Nature  never  is. ' '  This  was  the 
doctrine  preached  by  Sir  Michael  Foster  in  his  address  at 
Dover  as  President  of  the  British  Association.  It  is  the  first 
principle  of  science.  Mathematics  neglects  the  infinitely 
small.  Common  sense  is  content  with  an  approximation  to 
the  truth,  trusting,  quite  justifiably  in  the  hurry  of  business, 
that  much  that  it  does  not  understand  is  capable  of  explana- 
tion. Science  recognises  no  negligible  quantity.  "You 


FIRST    PRINCIPLES  23 

don't  seem  astonished,  Mr.  Brown,  at  the  wonderful  nar- 
rations of  Deacon  Smith,"  said  Widow  Jones  to  one  of  two 
Yankees  who  were  lounging  in  front  of  her  fire.  * '  No, 
ma'am,  I'm  a  liar  myself,"  was  the  laconic  reply.  One  of  the 
first  things  which  science  recognises  is  that  all  men  are  liars. 
We  all  inherit  a  tendency  to  believe  in  and,  still  more 
strongly,  to  narrate  the  marvellous.  It  is  the  business  of 
the  man  of  science  to  shake  such  narrations  with  simple 
straightforward  questions,  to  check  them  again  and  again 
by  pointing  out  gaps  in  evidence  or  barriers  against  evidence 
which  the  narrator  cannot  cross. 

We  have  already  insisted  that  consciousness  can  be  inves- 
tigated only  by  consciousness.  The  senses  are  the  "win- 
dows of  the  mind"  which  give  upon  the  outside  world. 
Consciousness  is  not  force.  We  cannot  find  a  place  for  it  in 
the  balance-sheet  of  the  body.  When  we  have  audited  its 
accounts — have  debited  the  body  with  x  +  y  units  of  poten- 
tial energy  received  in  food,  and  have  placed  to  its  credit 
x  units  of  muscular  force  and  y  units  of  heat ;  when  we 
have  debited  it  with  a  -f-  )3  units  of  force  received  as  vibra- 
tions by  the  endings  of  nerves  in  the  sense-organs,  and  have 
credited  it  with  a  units  of  nerve  force  transmitted  to  the 
muscles  through  the  central  reflex  mechanism,  and  /3  units 
consumed  in  effecting  molecular  rearrangement  of  nerve- 
tissue;  we  still  find  no  place  for  consciousness.  We  cannot 
enter  as  ' '  concerned  in  the  production  of  conscious ' '  £ 
of  the  force  received.  And  yet,  although  consciousness 
cannot  be  identified  with  either  matter  or  force,  it  is  at  least 
as  real  as  either.  Wrhen  we  think  of  the  universe,  these 
three  realities  stand  forth  :  matter,  force,  consciousness. 
And  as  we  know  that  matter  is  indestructible,  it  seems  to 
us  impossible  to  escape  the  conclusion  that  consciousness 
is  indestructible  also.  We  can  no  more  conceive  of  it  as 
coming  out  of  nothing  or  fading  into  nothingness  than  we 
can  conceive  of  matter  or  of  force  coming  into  existence 
or  ceasing  to  be.  And  as  the  portion  of  matter  which  con- 


24  AN   INTRODUCTION   TO   SCIENCE 

stitutes  our  bodies  is  but  a  part  of  a  universe  of  matter,  and 
as  the  force  with  which  we  are  endowed  is  but  a  part  of  a 
universe  of  force,  so,  too,  our  consciousness  seems  to  be 
but  a  part  of  universal  consciousness. 

How  are  we  to  know  anything  about  the  universal  con- 
sciousness unless  by  revelation  ?  Science  has  stopped  short 
at  the  confines  of  the  knowable.  This  is  its  boundary.  It 
cannot  proceed  farther  than  the  five  senses.  They  give 
it  no  support  in  a  region  where  there  are  no  phenomena 
to  be  observed.  The  external  relations  of  consciousness 
are  known  only  to  religion.  Religion,  which  must  from  the 
necessities  of  the  case  be  expressed  in  human  language, 
is  represented  by  phenomena  of  the  physical  universe.  To 
some  minds  the  representation  carries  a  more  real,  to  others 
a  more  allegorical  meaning,  but  the  form  in  which  it  carries 
most  meaning  is  to  the  individual  most  true.  Science  can 
throw  no  light  upon  religion  in  its  inner  sense.  It  cannot 
criticise  religion.  It  can  only  recognise  the  existence  of 
the  other  world  and  retire  to  its  own  domain  ;  and  as  our 
subject  is  science,  it  is  our  duty  also,  having  brought  our 
argument  to  its  proper  limit,  to  cease  from  any  attempt  to 
follow  it  farther. 

But  what  of  the  alleged  incursions  of  the  spirit-world 
into  the  physical  universe ;  ghosts  making  themselves  sen- 
sible to  eye  and  ear,  spirit-rappings,  table-turning  without 
the  application  of  adequate  muscular  force,  materializations, 
and  all  the  other  hocus-pocus  of  theosophy?  Has  science 
no  right  to  resent  the  trespass  ?  Of  course  it  has.  As  soon 
as  the  phenomenon  becomes  a  physical  phenomenon  it  is 
the  duty  of  science  to  investigate  it.  It  is  the  duty  of  the 
man  of  science  to  adopt  such  tests  as  Faraday  adopted, 
to  fix  a  false  top  to  a  table  with  a  manometer  between  it 
and  the  original  top,  and  to  show  that  the  fingers  which 
were  supposed  to  resist  the  temptation  to  push  exercised 
the  exact  amount  of  force  required  to  move  the  table  ;  to 
devise  the  "control  experiment,"  which  has  baffled  so  many 


FIRST   PRINCIPLES  25 

clairvoyants  ;  to  search  the  files  of  telegrams  until  Madame 
Blavatsky's  communications  with  India  are  found  to  be 
transmitted  by  no  agency  more  marvellous  than  the  electric 
telegraph.  It  is  not  for  the  man  of  science  to  adopt  an 
attitude  of  either  credulity  or  incredulity.  Into  the  world 
of  consciousness  he,  as  a  man  of  science,  does  not  claim 
admission  ;  but  matter  and  force  are  within  his  province, 
and  his  duty  to  investigate  all  phenomena  which  they 
exhibit  is  not  in  any  way  affected  by  the  pretended  mystery 
of  the  agencies  which  evoke  them. 

The  Relation  of  Philosophy  to  Science.— In  con- 
sidering the  boundaries  of  science,  wre  have  already  antici- 
pated some  of  the  reflections  to  which  this  subject  naturally 
gives  rise ;  and  we  shall  now  be  obliged,  owing  to  the 
uncertainty  of  definition  of  the  term  Philosophy,  to  return 
to  some  extent  over  the  ground  already  traversed.  In  the 
present  day  the  term  Philosophy  is  used  in  a  relative  sense. 
Herbert  Spencer  describes  it  as  "  knowledge  of  the  highest 
degree  of  generality."  The  search  for  knowledge  which 
is  absolutely  general  has  been  abandoned.  Since  pure 
thought,  independent  of  any  particular  application,  depends 
upon  absolute  knowledge,  it  also  is  a  logical  fiction.  It 
is  the  process  of  abstraction  carried  to  the  power  of  n. 
Absolute,  thought  would  be  no  thought,  the  sleep  of  the 
intellect ;  just  as  absolute  knowledge  would  be  no  knowl- 
edge, ignorance  :  Nihil  est  intellectu  quod  non  prius  fuerit 
in  sensu.  It  is  easy  to  show,  with  Leibnitz  and  Locke,  that, 
however  far  thought  may  be  removed  from  the  basis  of 
observation  upon  which  it  started,  its  independence  of 
observation  is  only  a  question  of  degree. 

Reasoning  concerning  the  Absolute  and  the  Infinite  soon 
leads  to  paradox.  An  old  friend  of  Professor  de  Morgan 
told  me  that,  when  the  professor  was  harassed  by  people 
who  pressed  him  to  explain  things  which  he  felt  that  he 
could  merely  assert  or  deny,  he  would  murmur  :  ' '  The 
infinite  circle  is  bounded  by  an  infinite  straight  line."  The 


26  AN   INTRODUCTION   TO    SCIENCE 

boundaries  of  science  and  philosophy,  when  pressed  to 
their  ultimate  terms,  may  be  summed  up  in  the  same  way: 
"Infinite  science  is  bounded  by  philosophy,"  and  vice 
versa. 

\Ye  may,  of  course,  set  aside  as  immaterial  to  our  sub- 
ject the  sense  which  was  given  to  the  term  Philosophy  by 
the  Stoics  —  a  system  of  the  principles  of  action  which 
regulate  conduct  —  a  sense  which  still  in  its  popular  use 
clings  to  the  name.  The  only  meaning  in  which  philosophy 
has  any  bearing  upon  our  subject  is  that  in  which  it  stands 
for  an  organised  system  of  thought  of  the  most  abstract 
kind ;  thought  which  pierces  as  far  as  possible  through  the 
visible  husk  of  things  into  the  principles  which  determine 
their  particular  manifestations.  From  the  earliest  times 
thinkers  have  not  been  content  to  believe  that,  when  Man 
knows  the  utmost  that  can  be  known  about  phenomena, 
he  knows  the  realities  of  which  phenomena  are  the  mani- 
festations. Something  unknowable  is  sought  for  behind  the 
outward  mask  which  alone  is,  or  ever  will  be,  seen  by 
Man  —  a  universal  principle,  a  soul,  a  deity,  "an  actuality 
lying  behind  appearances." 

\Yith  the  philosophy  of  the  Absolute  a  man  of  science 
has  no  concern.  His  province,  as  man  of  science,  ends  at 
the  zone  in  which  hypothesis  can  no  longer  be  .checked 
by  observation  or  experiment.  For  working  purposes  he 
accepts  the  axiom  that  "all  statements  which  cannot  be 
confronted  with  objective  tests  are  false."  If  no  test  can 
be  applied  to  them  they  are  equally  true  and  false  to  him. 
Thinking  about  them  is  a  waste  of  time.  Science  is  the 
elaborated  product  of  observation. 

Yet,  at  the  same  time,  the  man  of  science,  in  common 
with  thinkers  trained  in  other  ways,  knows  that  he  has  two 
sources  of  information — his  senses  and  his  inner  conscious- 
ness. When  reflecting  upon  the  mental  processes  by  which 
the  materials  supplied  by  the  senses  are  worked  into 
thought,  the  Mind  is  watching  its  own  activities.  By  self- 


FIRST   PRINCIPLES  27 

study  a  man  acquires  a  knowledge  of  knowing,  thoughts 
about  thinking.  He  knows  that  he  possesses  consciousness. 
It  is  not  that  he  is  consciousness  —  merely  a  concomitant 
of  a  certain  kind  of  nerve-activity.  He  owns  a  conscious- 
ness which  he  can  direct  and  control ;  from  which  it  fol- 
lows that  there  is  a  He  to  own  it.  But  the  two  sources  of 
information  must  never  be  confused.  The  lines  of  thought 
for  which  the  external  and  the  internal  worlds  supply 
materials  are  parallel,  and  neither  diverging  nor  converg- 
ing lines.  A  man's  consciousness  gives  him  no  more  infor- 
mation with  regard  to  his  science  than  his  senses  give  him 
with  regard  to  his  consciousness.  The  two  worlds  are 
absolutely  and  permanently  distinct. 

Science  prosecutes  its  researches  to  the  confines  of  the 
observable.  Self-analysis  is  carried  to  the  limits  of  con- 
sciousness. Each  line  of  research  is  abandoned  with  a 
sense  that  there  is  something  beyond.  Beyond  the  know- 
able,  the  unknowable.  Beyond  the  self-conscious,  the  All- 
conscious.  It  is  in  this  beyond  that  the  philosophy  of  the 
Absolute  weaves  its  system.  It  is  this  beyond  that  religion 
seeks  to  explain.  Religion  claims,  indeed,  that  the  world 
behind  sense  and  the  world  beyond  consciousness  are  one. 

"We  know  nothing  beyond  our  simple  ideas — which  we 
are  not  at  all  to  wonder  at,  since  we,  having  but  some 
superficial  ideas  of  things,  discovered  to  us  only  by  the 
senses  from  without,  or  by  the  mind  reflecting  on  what  it 
experiments  in  itself  within,  have  no  knowledge  beyond 
that,  much  less  of  the  internal  constitution  and  true  nature 
of  things,  being  destitute  of  faculties  to  attain  it.  And,  there- 
fore, experimenting  and  discovering  in  ourselves  knowledge 
and  the  power  of  voluntary  motion  as  certainly  as  we 
experiment  or  discover  in  things  without  us  the  cohesion 
and  separation  of  solid  parts,  which  is  the  extension  and 
motion  of  bodies,  we  have  as  much  reason  to  be  satisfied 
with  our  notion  of  immaterial  spirit  as  with  our  notion  of 
body,  and  the  existence  of  the  one  as  well  as  the  other. 


28  AN  INTRODUCTION   TO    SCIENCE 

For,  it  being  no  more  a  contradiction  that  thinking  should 
exist  separate  and  independent  from  solidity  than  it  is  a 
contradiction  that  solidity  should  exist  separate  and  inde- 
pendent from  thinking,  they  being  both  but  simple  ideas, 
independent  one  from  another ;  and  having  as  clear  and 
distinct  ideas  in  us  of  thinking  as  of  solidity,  I  know  not 
why  we  may  not  as  well  allow  a  thinking  thing  without 
solidity,  i.  e.,  immaterial,  to  exist,  as  a  solid  thing  with- 
out thinking,  i.  e.,  matter,  to  exist ;  especially  since  it  is 
no  harder  to  conceive  how  thinking  should  exist  without 
matter  than  how  matter  should  think.  For  whensoever  \ve 
would  proceed  beyond  these  simple  ideas  we  have  from 
sensation  and  reflection,  and  dive  farther  into  the  nature 
of  things,  we  fall  presently  into  darkness  and  obscurity, 
perplexedness  and  difficulties  ;  and  can  discover  nothing 
farther  but  our  own  blindness  and  ignorance.  But  which- 
ever of  these  complex  ideas  be  clearest,  that  of  body  or 
immaterial  spirit,  this  is  evident,  that  the  simple  ideas  that 
make  them  up  are  no  other  than  what  we  have  received 
from  sensation  or  reflection  ;  and  so  is  it  of  all  our  other 
ideas  of  substances,  even  of  God  Himself."* 

It  is  only  when  entirely  freed  from  trancendentalism  that 
philosophy  has  any  part  to  play  in  the  advance  of  science, 
and  probably  it  would  conduce  to  clearness  of  thought  if 
the  term  were  to  disappear  altogether  from  the  scientific 
vocabulary.  Nevertheless  the  adjectives  "scientific"  and 
"philosophical "  usefully  distinguish  two  aspects  of  thought ; 
aspects  which  contrast  in  degree,  although  not  in  kind.  By 
scientific  is  meant  the  slow  advance  from  observation  to 
observation,  the  stability  of  each  fact  being  tested  and 
retested  before  thought  trusts  it  to  support  the  simplest 
theory ;  by  philosophical  is  meant  the  leap  beyond  the 
reach  of  ascertained  fact  and  the  subsequent  search  for  facts 
in  justification  of  speculation.  Philosophical  speculation 

*Locke,  "  Essay  concerning  Human  Understanding,"  Book  II.,  Chap, 
xxiii  ,  Sect.  32. 


FIRST   PRINCIPLES  29 

takes  a  plunge,  as  it  were,  into  the  uncertain  sea,  trusting 
to  reach  firm  ground  again  before  its  power  of  swimming 
is  exhausted ;  whereas  science,  more  cautious,  builds  solid 
facts  into  a  causeway,  and  never  allows  the  waves  of  uncer- 
tainty to  wet  it  above  the  ankles.  But  yet  it  is  a  question 
only  of  degree,  for  the  shortest  hypothesis  which  bridges 
across  from  fact  to  fact  is  in  itself  as  wanting  in  solidity  as  the 
widest  generalisation  of  which  the  human  mind  is  capable  ; 
and  the  widest  generalisation  is  equally  with  the  narrowest 
but  an  attempt  to  unite  isolated  territories  of  solid  fact. 
The  process  of  reasoning  is  in  the  two  cases  the  same  ; 
but  the  one  regards  certainty  as  the  chief  desideratum,  the 
other  aims  at  enunciating  the  theory  which  will  embrace 
the  greatest  number  of  phenomena  within  its  scope.  ' '  Scien- 
tific "  and  "  philosophical "  are  not  antithetical  terms,  for 
there  can  be  no  opposition  between  science  and  philosophy. 
It  would  be  easy  to  show,  seeing  that  the  scientific  process — 
the  process  of  induction — is  carried  to  the  utmost  confines 
of  thought,  that  all  products  of  human  intelligence  deserve 
to  be  classed  as  science ;  or,  on  the  other  hand,  since 
knowledge  acquires  value  only  when  worked  into  thought, 
the  whole  field  of  science  might  with  equal  propriety  be 
assigned  to  philosophy. 

The  Senses  the  Agents  of  the  Mind.— From  very 
ancient  times  it  has  been  recognized  that  the  great  brain  or 
cerebrum  is  the  seat  of  consciousness,  thought  and  volition. 
It  may  now  be  asserted  that  the  cortex,  or  sheet  of  grey 
matter  which  covers  the  cerebral  hemispheres,  is  alone  con- 
cerned with  these  processes.  The  cortex  cerebri  is  therefore 
the  apparatus  of  mind.  Prior  to  1870  the  brain  was  a 
mysterious  organ,  forbidding  further  physiological  explora- 
tion. It  was  thought  that  it  functioned  "  as  a  whole, ' '  and 
any  attempt  to  analyse  the  constituent  physiological  pro- 
cesses of  the  act  of  thinking  was  looked  upon  as  frivolous  if 
not  sacrilegious.  Our  mode  of  viewing  the  apparatus  of 
thought  has  undergone  a  great  change  since  1870.  Since 


30  AN    INTRODUCTION   TO    SCIENCE 

then  it  has  been  shown — (i)  that  stimulation  of  particular 
areas  of  the  cortex  results  in  definite  movements,  while 
removal  of  the  said  areas  is  followed  by  paralysis  for  these 
movements,  and  (2)  that  almost  the  whole  of  the  cortex  can 
be  mapped  into  territories  which  are  occupied  by  the  several 
senses.  It  is  true  that  a  region  is  left  in  the  front  of  the 
brain  corresponding  with  the  forehead,  which  cannot  at 
present  be  associated  wTith  either  movement  or  sensation  ; 
but,  although  its  functions  are  unknown,  there  are  ample 
grounds  for  believing  that  the  mind  makes  no  greater  use  of 
this  region  than  of  the  regions  behind  it.  For  instance,  this 
anterior  region  may  be  found  to  be  healthy  in  cases  in  which 
the  mind  was  most  hopelessly  deficient  or  deranged  ;  or,  on 
the  other  hand,  this  region  may  be  extensively  injured,  and 
yet  no  mental  deficiency  be  recorded.  This  does  not  show 
that  it  is  not  concerned  with  mind,  since  the  same  may  be 
said  of  every  other  region  of  the  cortex,  but  it  proves  that  it 
is  not  the  special  or  chief  seat  of  mind. 

If  the  brains  of  animals  which  are  conspicuous  for  the 
great  acuteness  of  one  particular  sense,  or  for  its  abeyance, 
be  examined,  it  is  easy  to  see  which  parts  of  the  brain  are 
associated  with  this  sense  ;  and  it  is  possible  to  select  such  a 
series  of  animals  as  will  show  an  excessive  or  deficient 
development  of  each  of  the  five  senses.  A  dog  shows  a 
vast  development  of  the  sense  of  smell ;  a  marine  mammal 
is  totally  destitute  of  this  sense,  for  it  is  obvious  that  smell  is 
a  sense  which  cannot  be  employed  under  water.  The  eye 
is  as  useless  underground  as  the  nose  under  water,  and  it 
may  consequently  atrophy  completely,  as  in  the  mole.  An 
otter,  twisting  in  and  out  among  the  snags  and  roots  which 
border  a  dark  brown  peat-stained  mountain  stream,  searches 
for  the  fish  which  "sulk,"  to  use  a  piscatorial  term,  under 
the  overhanging  banks.  Its  eye  is  almost  as  useless  to  the 
otter  as  its  nose,  and  it  consequently  relies  for  information 
chiefly  upon  the  extraordinarily  sensitive  bristles  of  its  cheek 
and  lip.  Again,  anyone  who  watches  a  cat  will  see  that  its 


FIRST    PRINCIPLES  31 

tactics  when  hunting  are  quite  different  to  those  of  a  dog. 
Its  nose  gives  it  general  information  of  the  proximity  of 
mice,  but  it  never  follows  a  trail.  Its  ear  tells  it  with  such 
precision  when  to  spring  and  in  what  direction,  that  the 
legend  has  sprung  up  that  a  cat  can  "see  in  the  dark."  In 
truth  its  eye,  which  aids  in  hunting  in  daylight,  is  of  much 
less  importance  to  it  when  darkness  approaches  than  its 
cheek-bristles,  which  save  it  from  contact  with  passive 
objects,  and  its  ear,  which  tells  it  when  it  is  approached  by 
anything  that  moves. 

While  carnivora  trust  either  to  the  sense  of  smell,  or,  like 
the  felidae,  to  the  senses  of  hearing  and  smell  in  following 
their  prey,  herbivora  trust  to  the  eye  for  information  as  to 
the  proximity  of  their  pursuers.  Observations  of  their  habits 
would  enable  us  greatly  to  extend  the  list  of  animals  in 
which  one  or  other  of  the  senses  is  unusually  efficient  or 
unusually  deficient.  Those  named  above  are  but  typical 
examples,  and  if  any  one  of  them  which  exhibits  during  life 
a  great  reliance  upon  a  particular  sense  be  examined 
anatomically,  it  will  be  found  that — (i)  the  organ  which 
serves  this  sense  is  obviously  well  developed  ;  (2)  the  nerve 
which  connects  the  sense-organ  with  the  central  nervous 
system  contains  an  unusually  large  number  of  fibres ;  (3) 
that  the  territory  in  the  brain  which  is  allocated  to  this  sense 
is  more  than  usually  extensive. 

Anatomy  and  physiology  have  therefore  in  a  remarkable 
way  confirmed  the  truth  of  Leibnitz'  dictum,  "There  can  be 
nothing  in  the  intellect  which  has  not  reached  it  through  the 
senses."  Metaphorically  speaking,  science  has  given  an 
objective  value  to  the  intellect.  It  has  enabled  us  to  speak 
of  the  size  and  form  of  the  brain  when  we  indicate  the 
extent  and  quality  of  the  mind  which  uses  it.  Five  instru- 
ments are  played  in  the  orchestra  of  thought :  smell,  vision, 
hearing,  taste  and  feeling,  the  last  named  being  an  organ 
with  several  claviers.  Vibrations  of  various  kinds  strike  the 
keys  of  these  sense-organs.  Those  which  call  forth  sensa- 


32  AN  INTRODUCTION  TO    SCIENCE 

tions  of  smell  and  taste  are  limited  to  the  orbits  of  the 
molecules  of  odorous  and  sapid  substances.  Those  which 
stimulate  the  organs  of  vision  and  hearing  have  an  unlimited 
progression  in  space,  the  waves  of  light  being  ' '  up  and 
down ' '  vibrations,  which  follow  one  another  at  the  rate  of 
hundreds  of  billions  to  the  second,  whereas  sound  is  con- 
veyed in  the  form  of  "to  and  fro "  pulsations,  which  are  not 
appreciated  by  the  ear  if  they  are  more  rapid  than  40,000  to 
the  second.  An  analysis  of  the  several  kinds  of  stimuli 
which  affect  the  sense-organs  of  the  skin  would  take  up  more 
space  than  we  have  to  spare. 

Light  was  first  thrown  upon  the  mode  of  working  of  the 
cortex  by  the  discovery  that  by  stimulating  it  with  an  electric 
current  definite  movements  can  be  invariably  evoked.  This 
is  commonly  expressed  by  saying  that  it  contains  centres  of 
movement.  The  discovery  of  its  allocation  among  the 
several  senses  was  made  later.  The  question  of  the  relation 
as  cause  and  effect  of  the  sensations  which  are  received  in 
the  cortex  and  the  movements  which  are  originated  by  it  is 
one  of  great  complexity.  Nevertheless,  taking  the  most 
general  view  of  the  cortex  as  the  organ  of  the  mind,  we  may 
safely  say  that  it  is  the  nerve-tissue  in  which  sensations  are 
received  and  become  conscious  perceptions,  and  from  which 
nerve-impulses  for  the  evoking  of  muscular  actions  are 
despatched.  In  sleep  and  some  other  unconscious  condi- 
tions these  two  terminals  are  placed  in  connection  ;  sensa- 
tions flow  over  into  movement  by  reflex  action.  During  the 
waking  state  the  mind  intervenes.  Sensations  become  per- 
ceptions, and  the  mind,  taking  cognizance  of  these  presenta- 
tions of  sense,  decides  whether  they  shall  flow  over  at  once 
into  action  or  whether  they  shall  be  stored  as  memories  for 
future  use ;  whether,  flowing  over  with  very  little  reinforce- 
ment, they  shall  produce  an  obviously  correlated  action,  or 
whether,  by  combination  with  dormant  perceptions,  they  shall 
be  expressed  in  a  sequence  of  movements  which  seems, 
until  it  is  minutely  analysed,  to  be  too  complicated  to  result 


FIRST    PRINCIPLES  33 

from  a  single  presentation  of  sense.  Whether  or  not  the 
mind  perceives  them,  however,  all  sensations  produce  their 
effects  upon  the  organism.  Sensations  which  the  mind  per- 
ceives are  the  raw  materials  which  it  works  into  a  product  by 
which  intelligence  is  made  manifest.  Mental  action  is  a 
weaving  of  sensations  into  a  pattern,  and  the  expression 
of  this  pattern  in  act  or  thought. 

If  we  try  to  figure  to  ourselves  the  mental  activities  of  any 
animal,  we  recognise  at  once  that  its  thoughts  must  take  the 
colour  of  the  sense  by  which  they  are  chiefly  prompted.  A 
dog,  for  example,  does  not  recognise  "a  family  likeness," 
but  a  family  smell.  In  a  day  of  happy  wandering  down  the 
village  street  and  through  the  lanes  it  pays  no  attention  to 
the  picturesque.  As  it  lies  in  front  of  the  fire,  reviewing  the 
experiences  of  the  day,  it  recalls  a  long  succession  of  sugges- 
tive smells.  It  is  the  cheek-bristles  of  the  otter  which 
vibrate  with  excitement  as  it  remembers  the  slippery-sided 
salmon  it  nearly  mistook  for  an  alder-root.  The  cat  twitches 
its  ears  as  it  dreams  of  bursting  unannounced  into  a 
seminary  of  mice.  If  we  wish  in  any  degree  to  realise  what 
our  thoughts  would  be  like  if  we  were  to  exchange  our  brain 
for  the  brain  of  some  other  animal,  we  must  ask  first : 
Which  of  the  five  sense-organs  is  the  one  through  which 
this  particular  animal  chiefly  looks  out  upon  the  world? 

Before  we  set  out  to  explore  the  world  it  is  well  that  we 
should  inquire  into  the  credentials  of  the  agents  upon  whom 
we  shall  depend  for  information.  These  agents  are — 

1.  The  Nose. — A  poor  thing  to  depend  upon,  and  turned 
to  base  uses.  We  rely  upon  it  chiefly  to  tell  us  when  we  are 
near  drains  or  other  receptacles  for  matter  which  experience 
has  shown  us  to  be  noxious.  We  speak  of  such  smells  as 
"nasty. "  "  Nice  smells "  are  not  for  the  most  part  nice  in 
themselves,  but  scents  which,  like  musk,  frangipanni,  aro- 
matic oils,  etc. ,  are  peculiarly  efficient  in  antagonising  nasty 
smells  ;  for  the  sense  of  smell  in  Man  is  almost  useless  for 
analysis  ;  it  can  hardly  distinguish  one  scent  in  the  presence 


34  AN   INTRODUCTION   TO    SCIENCE 

of  another,  still  less  can  it  resolve  a  combination  into  its 
constituent  odours.  How  different  it  must  be  in  the  dog, 
which  can  trace  its  master's  footsteps  out  of  a  thousand,  or 
follow  them  even  when  the  master,  to  hide  his  trail,  puts  oil 
of  bergamot  on  his  boot-soles.  By  the  time  middle  life  is 
reached,  even  the  small  portion  of  our  brain  which  is 
allocated  to  the  sense  of  smell  shows  atrophic  degeneration, 
proving  that  the  sense  is  disappearing — as  we  might  discover 
by  careful  observation  ;  although  as  a  general  rule,  from 
force  of  habit  and  because  we  hardly  ever  call  it  into  action, 
we  suppose  that  we  still  retain  it.  Its  ever  fading  pictures 
still  delight  or  shock  us. 

Stimulation  of  the  olfactory  membrane  gives  a  ' '  massive 
sensation  ;"  it  is  not  marked  by  detail,  that  is  to  say.  It  is 
for  this  reason  that  scents  (and  the  same  is  true  in  a  less 
degree  of  tastes)  recall  scenes  in  a  way  which  other  sensa- 
tions cannot  do.  The  syringa  which  surrounded  the 
summer-house  in  which  we  played  as  children,  the  jasmine 
beneath  our  bed-room  window,  the  smell  of  warm  pepper 
with  which  a  particular  sausage-factory  reeked — we  never 
smell  syringa,  jasmine,  pepper,  without  recalling  these 
vividly  toned  scenes.  Anything  seen  with  the  eye  or  heard 
with  the  ear  would  have  characters  of  its  own,  but  the  scent 
of  syringa  is  the  same  whenever  and  wherever  we  smell  it, 
and  it  must  always  be  the  background  to  the  first  strongly 
associated  visual  picture. 

The  olfactory  membrane  responds  to  the  particles  of 
certain  chemical  substances  which  have  a  comparatively 
rapid  proper  vibration,  especially  such  substances  as  the 
essential  oils.  It  cannot  answer  to  a  gas,  of  which  the 
atomic  weight  is  less  than  15,  nor  to  bodies  of  considerable 
atomic  weight,  such  as  the  salts  of  the  heavier  metals. 

Sight. — This  is  the  sense  upon  which  Man  chiefly 
depends  ;  and  there  is  no  reason  to  think  that  his  eye  is,  in 
its  range  of  distance  from  objects  near  at  hand  to  objects  on 
the  horizon,  its  power  of  distinguishing  detail,  or  the 


FIRST   PRINCIPLES  35 

accuracy  of  its  colour-vision,  surpassed  by  that  of  any  other 
animal.  Yet  the  eye,  considered  as  an  optical  apparatus,  is 
extremely  faulty;  the  several  refractive  media  are  not  cor- 
rectly centred,  and  are  guilty  of  spherical  and  chromatic 
aberrations,  besides  a  variety  of  minor  faults.  The  layer  in 
which  waves  of  light  are  converted  into  nervous  impulses 
(the  rods  and  cones)  is  on  the  back  of  the  retina,  so  that  the 
picture  is  more  or  less  obscured,  like  a  photograph  taken 
with  the  back  of  the  sensitised  paper  in  contact  with  the 
negative.  But  the  picture  which  the  Mind  sees  does  not 
present  the  imperfections  of  the  image  on  the  retina.  By 
force  of  training,  the  Mind  has  come  to  ignore  the  faults  of 
the  retinal  image.  It  does  not  take  cognizance  of  the  ' '  blind 
spot "  or  of  the  yellow  colour  and  double  refraction  of  the 
"yellow  spot,"  the  only  part  of  the  retina  which  is  suffi- 
ciently sensitive  for  "direct  vision."  Nor,  indeed,  can  the 
retina  be  said  to  be  very  sensitive,  since  objects  which 
subtend  an  angle  with  the  eye  of  less  than  60"  do  not  fall  on 
separate  "sensational  units"  of  its  surface.  They  fail  to 
give  rise  to  separate  sensations,  and  are  therefore  seen  not 
as  two  objects  but  as  one.  Since  the  retina  is  a  mosaic  of 
sensational  units,  every  apparently  continuous  line  is  really 
seen  as  a  succession  of  points.  Again,  it  is  far  from  being 
capable  of  responding  to  all  vibrations  of  light.  There  are 
vibrations  slower  and  longer  than  the  red  and  more  rapid 
and  shorter  than  the  violet  to  which  it  is  insensitive.  And 
within  its  range,  who  shall  say  that  it  gives  us  correct 
information  as  to  the  relative  wave-lengths  of  rays  of  light — 
the  quality  of  the  different  rays  which  we  distinguish  as 
colour?  The  rays  which  produce  the  visible  spectrum 
present,  except  for  certain  gaps  due  to  the  absorption  of 
Frauenhofer's  lines  by  the  sun's  atmosphere,  every  possible 
rate  of  vibration  from  381  billions  to  the  second  to  764 
billions  ;  but  the  eye  can  distinguish  them  only  as  they  coin- 
cide with  or  approximate  to  three  mean  rates.  It  groups 
them  as  red,  green,  violet,  or  combinations  of  these  three 


36  AN   INTRODUCTION   TO    SCIENCE 

colours  in  varying  proportions.  If,  for  example,  the  rays 
vibrate  at  the  rate  of  580  billions  to  the  second,  the  eye  says 
that  they  partake  equally  of  the  characters  of  red  and  green, 
with  a  very  small  trace  of  violet,  and  the  brain  gives  to  this 
combination  the  quality  of  yellow.  We  cannot  imagine 
what  the  sensation— the  colour— would  be  like  if  the  eye 
contained  a  mechanism  specially  sensitive  to  the  rays  which, 
when  stimulating  equally  the  red  mechanism  and  the  green 
mechanism,  are  judged  to  be  yellow. 

Hearing. — A  comparison  of  the  cochlea  of  the  human 
ear  with  that  of  animals  shows  that  Man  possesses  an  organ 
of  hearing  which  is  as  elaborate  in  structure  as  any  to  be 
found  in  the  animal  kingdom  ;  and  such  observations  as  are 
available  indicate  that  he  can  put  it  to  far  better  use  in  the 
analysis  of  sound  than  any  animal  can.  Indeed  the  most 
remarkable  characteristic  of  the  ear,  as  an  organ  for  discrim- 
inating sounds  of  different  wave-lengths,  is  its  almost 
unlimited  capability  of  improvement  under  training.  An 
untrained  savage  cannot  discriminate  a  difference  of  less 
than  a  semitone  between  two  notes,  whereas  a  trained 
musician  detects  a  discrepancy  of  one-thirtieth  of  a  semi- 
tone, or  even  less.  And  not  only  can  the  ear  discriminate 
minute  differences  in  rate  of  vibration,  but  it  can  in  a  very 
remarkable  degree  resolve  compound  waves  of  sound  into 
their  constituent  waves.  No  tone  which  reaches  the  ear  is  a 
pure  tone.  Upon  the  vibrations  of  a  certain  rapidity  which 
constitute  its  prime  tone  are  superposed  numbers  of 
harmonic  vibrations  of  rapidity  greater  than  that  of  the 
prime  tone  in  the  proportions  of  f ,  f ,  f ,  and  so  on.  The  ear 
detects  the  presence  of  these  overtones  and  recognises  their 
relative  preponderance  or  the  "quality"  of  the  note  pro- 
duced by  a  musical  instrument.  As  an  analytic  apparatus 
the  ear  is  far  more  efficient  than  either  of  the  other  sense- 
organs. 

Animals  have  little  need  of  the  power  of  analysing 
sounds.  To  a  cat  all  mice  squeak  alike,  we  may  presume  ; 


FIRST    PRINCIPLES  37 

the  cry  of  "Meat,  meat!"  suggests  but  one  idea,  though 
sung  to  diverse  tones  ;  emotions,  not  ideas,  take  possession 
of  its  soul  as  it  listens  to  its  lovers  as  they  serenade  it  with 
the  "song  without  a  tune."  Its  ear  fully  performs  its  func- 
tions if  it  discriminates  a  limited  number  of  widely  different 
sounds.  It  is  not  the  quality  of  the  sound  that  interests  an 
animal  so  much  as  the  direction  from  which  it  comes,  the 
distance  away  of  its  source,  and  the  amount  and  character 
of  the  intervening  substances  by  which  it  is  muffled. 

The  ear  gives  to  us  but  little  information  of  the  position 
in  space  of  the  source  of  sounds.  Our  external  ears,  instead 
of  being  long,  movable  trumpets  which  collect  sounds,  and  at 
the  same  time  show  their  direction,  are  immovable  append- 
ages which  may  be  lopped  off  without  appreciably  affecting 
the  value  of  our  organs  of  hearing.  Man  uses  the  ear  to  but 
a  slight  extent  as  an  organ  for  investigating  the  universe. 
He  enjoys  its  great  analytical  power  as  an  avenue,  not  to  the 
outer  world,  but  to  the  mind  of  his  fellow-man  as  expressed 
through  speech.  Its  external  movable  appendage  has  ceased 
to  be  of  importance,  but  the  analysing  apparatus  of  the 
cochlea  has  been  developed  until  it  can  distinguish  several 
thousand  different  tones.  The  enjoyment  of  music  is  a 
remarkable  illustration  of  the  store  which  Man  sets  upon  his 
power  of  distinguishing  tones.  It  is  a  pleasure  to  use  this 
sensitive  mechanism  for  the  recognition  both  of  tones  in 
sequence  and  of  tones  in  combination.  Pure  tones  and  per- 
fect harmonies  are  listened  to  with  delight.  Imperfect 
harmonies,  which  are  difficult  to  analyse,  and  discords,  give 
pain  to  the  trained  ear.  This  is  not  the  place  to  consider 
the  meaning  of  music,  or  even  to  discuss  the  question  of 
whether  it  has  a  meaning,  until  by  association  we  assign  one 
to  it ;  but  it  is  allowable  to  point  out  in  passing  that  the 
pleasure  which  we  find  in  using  the  ear  for  the  analysis  of 
musical  sounds  confirms  our  statement  that  it  is  for  this 
purpose  that  Man  values  it.  Compare  for  a  moment  the  ear 
with  the  eye.  Several  pure  colours  flashed  at  the  same 

432234 


38  AN  INTRODUCTION   TO    SCIENCE 

instant  upon  the  retina  produce  but  one  mean  effect,  which 
might  have  been  produced  by  a  single  colour.  The  eye 
has  no  power  of  analysing  super-imposed  vibrations  of  light. 
A  harmony  of  several  colours  is  to  the  eye  what  a  melody 
is  to  the  ear.  But  the  eye  is  for  the  recognition  of  position 
in  space;  the  harmony  of  colours  must  be  stationary.  A 
•sequence  of  colours  is  not  only  not  enjoyable,  but  actually 
painful.  The  ear,  on  the  contrary,  reports  sequence  in 
time,  and  has  hardly  anything  to  do  with  position  in  space. 

Of  taste  and  of  "common  sensation"  we  need  say  but 
little.  The  former  has  so  personal  an  application  in  decid- 
ing what  we  shall  swallow  that  it  can  hardly  be  said  to  give 
us  any  information  as  to  the  properties  of  the  things  which 
belong  to  the  external  world  ;  the  information  reaches  our 
brain  only  at  the  moment  when  these  things  are  passing  into 
our  inside  selves  ;  while  the  latter  in  its  several  varieties  of 
sense  of  touch,  of  temperature,  of  pressure,  and  of  muscular 
exertion,  gives  us  information  chiefly  about  our  outside 
selves.  But  concerning  the  sense  of  touch  used  in  conjunc- 
tion with  the  sense  of  sight  much  might  be  said  ;  for  it  is  to 
this  cooperation  that  we  owe  all  that  we  know  as  to  the 
shape  and  position  of  the  objects  by  which  we  are  sur- 
rounded. To  take  a  simple  illustration  :  A  flash  of  light- 
ning illuminates  the  interior  of  a  darkened  room.  We  see 
it  as  a  space  bounded  by  walls  and  occupied  by  various 
solid  objects  ;  for  thus  we  interpret  the  image  formed  on  the 
two  retinae  of  our  eyes.  But  if  this  illuminated  room  were 
the  first  thing  seen  by  a  blind  man  it  would  convey  no  mean- 
ing to  his  mind.  His  sense  of  touch  would  have  told  him 
that  the  room  is  bounded  by  walls  and  that  it  contains  solid 
objects.  But  he  would  be  unable  without  training  to  cor- 
relate what  he  had  felt  with  what  he  now  saw.  His  eyes, 
used  now  for  the  first  time,  show  him  a  flat  picture ;  they 
give  him  no  information  regarding  the  third  dimension. 
Suppose  that  in  this  room  there  is  a  round  ball  resting  upon 
the  table.  The  man's  right  and  left  eyes  each  show  him  a 


FIRST    PRINCIPLES  39 

flat  picture  with  a  certain  incidence  of  light  and  shade  ;  but 
the  two  pictures  are  not  the  same.  The  right  eye  sees  more 
of  the  right  of  the  ball,  the  left  more  of  the  left.  Each 
picture  is  clear  in  outline,  yet  when  the  two  pictures  are 
superposed  it  is  only  at  the  two  poles  of  the  ball  that  the  out- 
lines of  shading  coincide.  Yet  to  those  who  have  always 
enjoyed  the  sense  of  sight  the  two  eyes  do  not  give  a  blurred 
picture  of  a  spherical  object,  even  though  it  be  illuminated 
but  for  an  instant  by  a  flash  of  lightning,  but  one  clear  in 
outline,  and  that  not  the  picture  of  a  flat  disc  but  of  a  solid 
sphere.  It  is  not  the  eye,  but  the  finger,  that  has  taught  us 
that  the  ball  is  solid.  We  have  learnt  to  associate  the  super- 
position of  two  non-coinciding  retinal  images  with  the 
extension  in  three  dimensions  of  an  object.  And  so  well 
has  our  Mind  learnt  this  lesson  that,  instead  of  seeing  a 
blurred  picture,  we  see  a  clear-cut  presentation  of  a  sphere. 
Artists  know  that  in  painting  a  round  ball  they  must  progres- 
sively increase  the  blurring  of  the  lateral  outline  from  the 
poles  to  the  equator ;  but  it  is  dangerous  to  go  far  in  this 
attempt  to  delude  the  eyes,  since  it  can  only  produce  the 
right  result  when  viewed  at  one  particular  distance  from  the 
canvas  ;  and  even  at  the  right  distance  the  two  eyes  soon 
find  out  the  fraud.  The  brain,  paying  attention  in  rapid 
alternation  to  the  images  transmitted  through  the  right  and 
left  eye  respectively,  discovers  that  they  are  both  blurred,  not 
clear  when  viewed  separately,  and  blurred  when  superposed. 
A  seascape  painter  is  reported  to  have  said  that  the  compli- 
ment to  his  artistic  skill  which  he  felt  most  keenly  was  paid 
him  by  an  uncultured  country  friend.  Attracted  to  his 
studio  by  a  heavy  thud  upon  the  floor,  he  entered  just  in 
time  to  see  his  friend's  boots  projecting  through  the  canvas 
of  his  last  and  most  successful  picture  of  a  deep,  clear, 
sun-lit  pool.  So  perfect  an  illusion  had  his  art  produced 
that  his  friend  had  given  way  to  a  natural  impulse  and 
"taken  a  header."  It  requires  but  little  physiological 
knowledge  to  enable  one  to  draw  the  conclusion  that  the  too 


40  AN   INTRODUCTION   TO    SCIENCE 

impressionable  connoisseur  of  seascapes  was  a  one-eyed 
man.  Art  cannot  deceive  the  two  eyes,  because  the  conflict 
of  their  presentations  which,  but  for  the  sense  of  touch, 
would  result  in  confusion,  has,  as  it  were,  added  a  new  sense 
of  the  position  and  shape  of  objects.  Thanks  to  the 
cooperation  of  eye  and  hand,  we  enjoy  a  sense  of  tacti-vision 
which,  by  long  training,  we  have  learnt  to  exercise  without 
sacrificing  the  sense  of  vision  pure  and  simple.  We  see 
with  the  clearness  of  the  lower  vertebrates,  birds,  reptiles 
and  fishes,  in  which  vision  is  mono-scopic,  although  we,  in 
common  with  monkeys  and  some  other  of  the  higher  verte- 
brates, have  acquired  the  power  of  stereoscopic  vision. 

Extension  of  the  Senses  by  Artificial  Aids.— Our 
senses  would  teach  us  little  of  the  world  in  which  we  live  if 
their  capacity  for  collecting  information  were  not  increased 
by  artificial  means.  By  placing  a  lens  or  a  system  of  lenses 
before  the  eye,  the  image  thrown  upon  the  retina  is  magni- 
fied and  our  power  of  distinguishing  detail  proportionately 
increased.  A  magnification  of  1,000  diameters  is  equivalent 
to  the  subdivision  of  each  "sensational  unit"  of  the  retinal 
surface  into  1,000,000.  By  collecting  waves  of  sound  in  a 
concave  reflector,  their  effect  upon  the  drum  of  the  ear  is 
intensified.  The  microphone  renders  audible  sounds  as 
faint  as  the  footfall  of  a  fly  or  the  beating  of  a  frog's  heart. 

More  important  than  the  apparatus  which  has  been 
devised  to  aid  the  senses  by  increasing  their  power  are  the 
instruments  which  have  been  invented  to  take  their  place — 
instruments  which  are  sensitive  to  a  degree  to  which  no 
organ  of  the  body,  however  aided,  could  attain.  Differences 
of  electricity  (it  seems  almost  strange  in  these  days  that  the 
body  is  not  equipped  with  any  organ  which  can  respond  to 
this  mode  of  motion!)  heat,  light,  colour,  weight,  chemical 
reactions  of  extreme  minuteness,  are  recognised  by  these 
instruments  of  precision  and — a  matter  of  even  greater  im- 
portance—they are  registered  in  a  permanent  form  so  that 
the  investigator  can  refer  to  them  at  his  leisure.  "  Science 


FIRST   PRINCIPLES  41 

is  measurement."  Much  of  the  credit  of  its  advance  is  due 
to  the  instrument-maker. 

A  list  of  the  instruments  of  precision  which  are  at  the 
service  of  workers  in  various  branches  of  science,  with  a 
comparative  statement  of  their  delicacy,  would  be  of  great 
interest.  But  such  a  list  would  be  misleading  unless  elab- 
orate explanations  were  given  of  the  conditions  under  which 
they  can  be  used  with  their  maximum  of  sensitiveness. 
For  example,  a  microscope  fitted  with  an  objective  of  -jVinch 
focal  length  and  an  eyepiece  multiplying  twelve  times 
will  give  a  magnification  of  3,000  diameters.  Yet  it  is  rarely 
that  so  high  a  power  can  be  usefully  employed.  Clearness 
of  definition  is  to  a  certain  extent  sacrificed  to  magnifica- 
tion ;  the  loss  of  "penetrating  power"  restricts  the  use  of 
such  a  combination  to  sections  of  the  extremest  thinness 
and  most  vivid  staining. 

Delicate  apparatus  for  testing  and  examining  objects 
exact  great  nicety  in  the  preparation  of  the  objects  for 
examination.  In  no  case  is  the  recent  improvement  in 
method  more  conspicuous  than  in  the  preparation  of  sections 
for  the  microscope.  Thirty  years  ago  the  histologist  placed 
the  specimen  of  which  he  wished  to  prepare  a  section 
between  two  pieces  of  cork  or  elder-pith,  and  cut  it  with  a 
razor  which  he  held  in  his  hand.  Now  he  has  microtomes 
of  many  patterns  to  choose  from.  He  may  embed  the 
object  in  celloidin,  soak  the  mass  with  water  and  cut  it 
frozen ;  or  he  may  embed  it  in  paraffin  and  cut  it  on  a 
riband-microtome— a  section-cutter,  so  named  because  the 
slices  of  paraffin  are  caused  to  adhere  to  one  another  at 
their  edges,  making  a  continuous  riband.  The  steady  hand 
upon  which  the  microscopist  used  to  pride  himself  is  no 
longer  required.  A  laboratory  boy  turns  a  handle,  or  the 
machine  is  connected  with  some  form  of  motor,  and  sections 
fall  away  from  the  razor  in  a  band  of  paraffin  which  can  be 
mounted  almost  automatically  on  glass  sides.  Nor  is  it 
necessary  to  mount  every  section.  The  machine  will  select 


42  AN   INTRODUCTION    TO    SCIENCE 

one  in  five  or  one  in  ten  and  thus  save  unnecessary  labour  in 
their  examination.  A  worm  an  inch  long  may  be  cut  into 
thirty  thousand  sections  by  an  assistant  who  has  no  knowl- 
edge of  anatomy,  and  comparatively  little  technical  training. 
And  not  less  remarkable  than  the  improvement  in  cutting 
sections  is  the  improvement  in  staining  them.  Again,  the 
investigator  can  delegate  to  an  assistant  technical  work 
which  used  to  consume  the  greater  part  of  his  own  time  ;  in 
this  work,  however,  there  is  hardly  a  limit  to  the  develop- 
ment, by  practice,  of  the  attendant's  skill.  Years  of  train- 
ing are  needed  to  make  him  master  of  some  of  the  more 
complicated  methods  of  colouring  sections  of  nerve-tissue. 
Closely  associated  with  improvements  in  methods  of 
manipulation  and  observation  is  the  increased  control  which 
the  observer  has  acquired  over  the  conditions  in  which  his 
observations  are  made.  He  can  vary  the  temperature  from 
the  point  at  which  hydrogen  becomes  a  solid  body,  within 
16  or  17  degrees  centigrade  of  absolute  zero  (below  which 
there  is  no  greater  cold,  for  molecular  motion  ceases 
altogether)  to  the  heat  of  the  electric  arc  in  which  the  most 
refractory  metal  passes  into  the  gaseous  state.  In  regard  to 
temperature,  therefore,  it  may  almost  be  said  that  his 
experiments  may  range  from  the  lowest  to  the  highest 
possible  limits.  Over  pressure,  electric  tension,  light,  his 
control  is  almost  equally  extensive.  He  is  no  longer  com- 
pelled, like  his  predecessors  in  the  field,  to  conjecture  that,  if 
it  were  possible  to  make  an  observation  under  certain  con- 
ditions, the  results  observed  would  be  thus  or  thus.  No 
sooner  does  his  argument  lead  him  to  infer  a  certain  result 
than  he  enters  his  laboratory,  and,  having  arranged  the 
conditions,  brings  his  hypothesis  to  the  bar  of  experience. 
Nay,  not  only  can  he  command  almost  every  combination  of 
conditions,  but  he  can  press  into  his  sen-ice  almost  every 
substance  which  can  exist.  Compounds  which  have  never 
been  found  in  nature  and  have  never  been  formed  by  art  are 
as  much  at  the  chemist's  disposal,  when  he  wants  them,  as 


FIRST   PRINCIPLES  43 

if  they  were  already  ranged  in  neatly  labelled  bottles  on  his 
shelves.  He  knows  their  formulae,  their  atomic  weight  and 
specific  heat,  and  much  regarding  their  properties,  before 
he  has  made  them,  and  whenever  it  may  suit  his  purpose  to 
make  them  the  steps  of  the  process  will  not  be  sought  for 
tentatively  and  with  misgiving,  but  followed  with  the  assur- 
ance that  they  must  inevitably  attain  the  desired  result. 

These  statements  as  to  the  power  of  science  are  mere 
platitudes.  We  stop  perhaps  too  frequently  to  wonder  at 
our  own  success  in  subjugating  nature  and  the  exceeding 
rapidity  of  its  recent  advance.  Yet  advance  brings  us  no 
nearer  to  the  end  of  our  labours,  for  the  more  we  know  the 
more  we  see  of  what  remains  to  be  known.  Every  problem 
laid  at  rest  gives  birth  to  two  new  problems  which  did  not 
present  themselves  to  the  mind  before.  Anyone  entering 
the  field  now  is  assured  of  work  to  do,  and  of  immense 
physical  resources  to  aid  him  in  doing  it.  But  probably  the 
attitude  of  mind  of  a  recruit  to  science  is,  or  should  be,  very 
different  now  to  that  of  the  long  army  of  fighters  who  have 
gone  before  him.  Here  and  there  we  may  pick  out  from 
amongst  the  pioneers  of  science  a  Cavendish,  a  Faraday,  a 
Robert  Brown,  whose  ambition  it  was  to  know  more  of 
things  near  at  hand  ;  but  the  greater  number  took  up  their 
work  with  anticipations  which  were  less  easily  to  be  ful- 
filled. To  go  back  no  farther  than  Huxley,  or  his  favourite 
model  Descartes,  the  study  of  science  was  undertaken  in  the 
hope  of  obtaining  a  wider  view  of  the  universe  and  a 
clearer  conception  of  what  does  or  does  not  lie  beyond, 
"to  learn  how  to  distinguish  truth  from  falsehood,  in  order 
to  be  clear  about  my  actions,  and  to  walk  sure-footedly  in 
this  life."  *  No  one  nowadays  can  hope  to  gain  a  compre- 
hensive view  of  science  as  a  whole,  still  less  to  abstract  from 
his  science  lessons  which  will  guide  him  in  shaping  his 


*"  Methods  and  Results."  Essays  by  T.  H.  Huxley,  p.  168.  A  quota- 
tion from  Descartes'  "  Discours  de  la  Methode  pour  bien  conduire  sa 
Raison  et  chercher  la  Verite  dans  les  Sciences." 


44  AN   INTRODUCTION    TO    SCIENCE 

course  in  life.  The  great  struggle  through  which  Huxley 
lived  is  over.  Science,  philosophy,  religion,  are  no  longer 
engaged  in  a  triangular  duel.  The  man  who  mines  for  gold 
is  in  no  way  concerned  with  the  analysis  of  the  emotions 
which  decide  a  rich  man  to  spend  it  upon  himself  or  to  give 
it  in  charity.  The  recruit  to  the  scientific  mine  must  be 
content  to  push  forward  his  adits  and  galleries  in  the  direc- 
tion in  which  gold  is  supposed  to  lie,  with  no  thought  of  the 
use  which  will  be  made  of  the  coined  metal,  and  no  expec- 
tation of  driving  his  tunnel  to  the  far  side  of  the  mountain 
and  catching  a  vision  of  the  beyond.  Nowadays  we  want  to 
know  because  we  want  to  know.  Philosophical  generalisa- 
tions, in  the  sense  which  still  clings  to  the  word  philosophy, 
of  a  guide  for  conduct,  are  no  longer  looked  for  from 
science. 


CHAPTER   II 
Classification 

COMTE  classed  the  sciences  as  abstract  and  concrete,  and 
this  subdivision  is  generally  followed.  Among  the  abstract 
sciences  Comte  placed  logic  and  mathematics,  which  treat 
only  of  the  form  in  which  phenomena  are  known  to  us, 
their  relations  in  quantity  and  their  sequence  in  thought, 
and  not  of  the  phenomena  themselves.  All  other  natural 
sciences  he  regarded  as  concrete. 

Herbert  Spencer  points  out  with  justice  that,  while  the 
abstractness  of  the  first  group  is  indisputable,  the  sciences 
of  the  second  group  are  not  wholly  concrete,  and  he 
removes  mechanics,  physics,  chemistry,  etc.,  into  an 
abstract-concrete  group,  because  they  lead  the  natural 
philosopher  to  the  purely  abstract  conception  of  force  per  se 
apart  from  its  manifestations  in  the  various  modes  of  motion 
— heat,  light,  electricity,  etc. 

But  this  distinction  is  too  philosophic,  if  we  may  use  the 
expression  without  offence,  for  scientific  thought.  Force, 
apart  from  its  manifestations,  is  only  a  conception,  although 
a  necessary  conception  of  the  human  mind.  It  has  its  start- 
ing point  in  the  mind,  and  expresses  the  attitude  of  the 
mind  towards  the  phenomena  of  which  it  takes  cognizance. 
If  we  try  to  conceive  of  force,  except  in  its  several  exhibi- 
tions, as  modes  of  motion,  we  soon  reach  the  vanishing 
point  in  which  the  material  of  thought  disappears,  and 
nothing  remains  but  its  clothing,  the  terms  in  which  thought 
is  expressed.  The  horny-brained  son  of  science  acquires  a 

(45) 


46  AN   INTRODUCTION    TO    SCIENCE 

habit  of  marching  every  claimant  for  a  place  in  the  world  ot 
facts  and  every  newly  derived  conclusion  up  to  his  dissect- 
ing table,  his  microscope,  his  balance,  with  a  curt  demand 
to  show  itself  for  what  it  is.  Small  wonder  if  he  grows  im- 
patient of  phantoms  which  walk  over  the  pan  of  his  most 
sensitive  balance,  past  his  photographic  plates,  and  through 
his  electroscopes  without  leaving  a  record.  He  doesn't 
deny  their  existence.  Why  should  he?  But,  without  looking 
up  from  his  work,  he  grumbles  that  it  isn't  his  business  to 
weigh  the  imponderable  or  to  measure  the  all-pervading. 

Physics  and  chemistry  deal  with  matter,  the  action  upon 
matter  of  force,  and  the  resolution  of  force  by  the  influence 
of  matter.  Sublimated  from  matter,  these  sciences  pass 
over  the  boundary  between  physics  and  metaphysics.  In 
their  abstract  form,  independent  of  phenomena,  they  resolve 
themselves  into  a  study  of  terms.  As  long  as  they  are 
based  upon  knowledge  they  are  concrete. 

It  is  somewhat  unfortunate  that  subjects  which  are  so 
little  congruous  as  mathematics  or  logic,  and  the  physical 
sciences,  must  be  included  under  a  general  designation  and 
classified  as  members  of  one  group.  Comte  in  his  classifi- 
cation was  not  using  the  terms  "  abstract "  and  "  concrete  " 
in  a  strictly  logical  way,  for  he  speaks  of  ' '  two  kinds  of 
natural  sciences— the  one  abstract,  general,  has  for  its  object 
the  discovery  of  the  laws  which  regulate  the  diverse  classes 
of  phenomena,  taking  into  consideration  all  the  cases  which 
can  be  conceived ;  the  others  concrete,  particular,  descrip- 
tive, which  are  sometimes  designated  as  the  natural  sciences 
properly  so-called,  consisting  of  the  application  of  these  laws 
to  the  effective  history  of  the  different  existing  things."  Her- 
bert Spencer  points  out  that  "abstract  "  and  "general "  are 
terms  which  cannot  be  compatibly  applied  to  the  same  class. 
"Abstractness-  means  detachment  from  the  incidents  of 
particular  cases.  Generality  means  manifestation  in  nu- 
merous cases,"  and  it  is  evident  that  the  comparative  iso- 
lation and  specialty  of  phenomena  or  their  generality  do 


CLASSIFICATION  47 

not  make  the  sciences  which  deal  with  them  concrete  or 
abstract. 

We  doubt  whether  anything  is  to  be  gained  by  classify- 
ing the  sciences.  They  are  mutually  dependent,  and  pass 
without  definition  one  into  the  other.  The  study  of  the 
formation  of  starch  in  a  plant  belongs  equally  to  chemis- 
try, botany  and  solar  physics.  But  while,  philosophically 
speaking,  there  is  but  one  Science,  the  cultivation  of  Science 
has  led  to  the  allocation  of  particular  parts  of  its  field  to 
particular  classes  of  men.  The  students  of  Science  can 
be  classified  with  more  success  than  the  subdivisions  of 
knowledge  which  they  severally  endeavour  to  make  their 
own. 

If  we  attempted  to  picture  the  tree  of  Knowledge  we 
should  sketch  it  somewhat  as  follows  :  At  the  base,  where 
it  rests  upon  the  ground,  ( i )  the  observation  of  the  physi- 
cal properties  of  familiar  objects.  The  description  of  these 
objects  and  the  comparison  of  their  properties  require  the 
exercise  of  thought.  The  endeavour  to  think  clearly  and 
to  express  consistently  gave  rise,  long  before  any  such 
science  was  formulated,  to  (2)  the  twin  trunk  Logic. 
Among  the  properties  of  the  objects  examined  were  cer- 
tain relations  in  number  and  extension.  As  soon  as  mere 
counting  and  measurement  were  accomplished,  and  num- 
bers and  extensions  were  imagined  apart  from  things 
numbered  or  measured,  a  thick  stem  branched  off  from 
the  tree  of  knowledge,  as  (3)  Mathematics.  The  bole  then 
divided  according  to  the  kinds  of  phenomena  observed 
into  (A )  the  study  of  the  movements  of  the  heavenly 
bodies,  Astronomy,  and  (B  )  the  study  of  the  earth.  The 
force  which  holds  the  heavenly  bodies  in  their  place  was 
subsequently  investigated  by  the  physicists,  and  their  con- 
stitution, as  shown  by  the  spectroscope,  by  the  chemists. 
The  earth  may  be  looked  at  as  a  whole,  (a)  Geology,  or 
in  its  constituent  parts.  The  parts  are  non-living  and  liv- 
ing. In  the  consideration  of  non-living  things  attention 


48  AN   INTRODUCTION    TO    SCIENCE 

may  be  paid  to  matter,  (0)  Chemistry ;  or  to  the  exhibi- 
tions of  force  through  matter,  (7)  Physics. 

As  the  study  of  the  several  modes  of  motion  is  to  the 
study  of  the  combinations  and  changes  of  state  of  matter,  so 
is  the  study  of  physiology  to  that  of  the  structure,  develop- 
ment, taxonomy  and  distribution  of  living  organisms,  includ- 
ing Man.  Biology  (5),  therefore,  includes  one  group  of 
subjects  and  (e)  Physiology  another ;  while  the  study  of 
function  leads  to  Psychology  (f),  and  this  to  (77)  Ethics 
and  (0)  Esthetics.  The  applied  sciences  must  take  their 
places  under  one  or  under  several  of  these  subdivisions. 
A  special  application  does  not  constitute  a  special  science. 
Nor  does  the  borrowing  of  materials,  or  methods  of  study, 
create  proprietorship  of  such  materials  or  methods.  Solar 
spectroscopy  is  not  astronomy,  nor  palaeo-botany  geology. 

Of  all  the  sciences,  if  each  is  looked  at  as  a  whole, 
astronomy  is  the  most  concrete.  Yet  before  Neptune  had 
been  observed  its  existence  was  inferred  by  Adams  as  the 
cause  of  the  perturbations  of  other  planets.  It  may  almost 
be  said  to  have  been  a  mathematical  product  in  Adams' 
mind.  Though,  of  course,  this  is  merely  a  figure  of  speech, 
for  the  cause  of  the  perturbations  was  at  all  times  in  his 
thoughts  a  concrete  thing ;  but  it  illustrates  the  way  in 
which  for  the  astronomer  the  heavenly  bodies  may  almost 
lose  their  objective  reality  apart  from  his  calculations. 

When  we  look  at  the  sciences  which  treat  of  the  world, 
its  constituents  and  inhabitants,  and  the  forces  to  which 
they  react,  we  see  that,  as  physics  becomes  abstract  in 
proportion  as  phenomena  are  left  behind  and  the  ideal 
conception  of  force  is  approached,  so  the  biological  sciences 
become  abstract  when  they  attempt  to  explain  the  nature 
of  life.  Life  is  to  the  manifestations  of  life  what  force  is 
to  the  manifestations  of  force.  No  definition  of  life  does 
more  than  specify  in  the  most  generalized  way  the  qualities 
which  distinguish  it  from  non-life.  When  Herbert  Spencer 
defines  it  as  "the  coordination  of  action"  he  does  not 


CLASSIFICATION  49 

bring  into  his  definition  the  source  or  cause  of  the  coordi- 
nation which,  from  the  philosophic  standpoint,  should  be 
of  the  essence  of  a  definition  of  life  as  distinguished  from 
living. 

Looked  at  as  comprehensive  of  all  living  things,  and 
not  as  peculiar  to  the  individual,  Life  might  be  better 
defined  as  "the  continued  adjustment  to  environment," 
since  upon  the  exhibition  of  this  tendency  to  adjust,  in  a 
higher  or  a  lower  degree,  depends  the  increase  in  the 
amount  of  life  in  every  particular  form,  or  its  decrease  and 
eventual  extinction ;  but,  again,  our  definition  is  a  gener- 
alised expression  for  the  manifestations  of  life  without 
reference  to  its  cause. 

In  attempting  to  distinguish  between  life  and  its  cause, 
we  are  coming  dangerously  near  to  the  old  doctrine  of 
"vitalism,"  with  all  its  barren  side-issues.  Is  it  not  better 
for  the  man  of  science  to  say,  "  Matter,  Force,  Life  are" 
without  attempting  to  conceive  what  they  are?  Let  him 
push  forward  his  investigations  as  far  as  observation  and 
reason  can  advance,  and  construct  hypotheses  as  to  what 
exists  beyond  the  outposts  of  knowledge,  so  long  as  the 
hypotheses  are  or  ever  can  be  verifiable,  because  such 
hypotheses  are  the  guiding  lines  of  further  research ;  but  a 
speculation  which,  from  the  very  nature  of  the  case,  is  un- 
verifiable  is  no  better  than  a  delusion. 

History  of  Science.— The  history  of  the  inductive 
sciences  was  brought  down  to  1846  by  Whewell  in  his 
second  edition.  No  single  man  is  competent  to  deal  with 
their  further  progress,  collectively,  since  that  date.  It  is  a 
tradition  with  the  writers  who  undertake  the  several 
branches  of  science  for  the  "Encyclopaedia  Britannica" 
that  they  should  preface  their  accounts  with  a  short  his- 
torical review.  Many  of  these  histories  are  excellently 
written  and  fascinating  to  read.  But  their  attraction  lies 
as  much,  perhaps,  in  the  record  of  the  mistakes  of  men  of 
former  time  as  in  their  discoveries  and  prophesies  since 


50  AN   INTRODUCTION   TO   SCIENCE 

verified.  The  pertinacity  with  which  men  cling  to  theories, 
ballasted  with  authority  rather  than  freighted  with  proof, 
seems  strange  in  these  days,  when  every  A.B.  is  his  own 
navigator  across  the  Sea  of  Science.  But  this  respect  for 
authority  must  be  allowed  for  in  studying  the  history  of 
knowledge.  It  is  not,  perhaps,  altogether  to  be  con- 
demned. Nor  should  the  errors  of  the  "men  of  old  times  " 
lead  us  to  undervalue  the  intellectual  force  of  the  men. 
The  tendency  of  us  moderns  is  perhaps  towards  immense 
knowledge  and  hasty,  ill-considered  generalisations,  mea- 
gre conclusions  from  abundant  data  rather  than  wide  con- 
clusions from  meagre  data.  It  is  the  inevitable  result  of  the 
vast  accumulation  of  knowledge  and  the  multiplication  of 
workers  engaged  in  research.  As  we  sometimes  wonder 
when  the  increase  of  traffic  in  front  of  the  Mansion  House 
will  lead  to  its  arrest,  so  are  we  tempted  to  ask  whether  the 
prosecution  of  research  will  not  some  day  cease  altogether, 
owing  to  the  multiplicity  of  workers  and  the  consequent 
impossibility  of  any  one  informing  himself  as  to  the  work 
which  others  have  done.  Every  man  who  is  engaged  in 
.  research  knows  the  sinking  of  heart  which  occurs  when  he 
decides  to  publish.  Publishing  involves  the  "  getting  up  of 
the  literature,"  which  perhaps  reveals  the  fact  that  all  that 
he  proposed  to  announce  to  the  world  has  been  anticipated 
by  some  one  else.  A  new  discovery  is  a  discovery  new  to 
me.  Its  interest  does  not  necessarily  vanish  when  I  find 
that  I  am  not  unique.  Nothing  but  the  prick  of  vanity  or 
the  pressure  of  self-interest  would  induce  a  scientific  worker 
to  face  the  drudgery  of  going  through  all  that  the  compe- 
tencies and  incompetencies  of  every  tongue  have  written 
on  his  subject.  The  quiet  academic  student,  who  recognises 
no  responsibility  towards  the  public  to  make  known  his  re- 
sults, and  feels  no  sense  of  gratification  in  substantiating  a 
claim  to  priority,  is  often  to  be  envied. 

The  history  of  human  progress  is  at  the  same  time  the 
history  of  error ;   but  both  progress  and  error  should  be 


CLASSIFICATION  51 

considered  in  relation  to  the  total  extent  of  knowledge  and 
the  opportunities  which  at  the  time  existed  of  checking 
speculation  by  observation.  If  it  were  possible  to  construct 
a  diagram  showing  the  extent  in  every  age  of  the  means  of 
attaining  knowledge,  and  the  deviations  from  truth,  and 
approaches  to  truth  of  natural  philosophers ;  and  then  to 
express  the  attainments  of  each  epoch  as  fractions,  with  the 
mean  truthfulness  as  numerator,  and  the  opportunities  of 
reaching  truth  as  denominator,  it  is  possible  that  the  result 
would  not  be  creditable  to  the  present  generation.  Anyone 
reading  the  history  of  science  should  form  such  a  mental 
diagram  in  which  the  man  with  unaided  senses,  the  Greeks, 
Romans,  Arabs,  scholars  of  the  seventeenth  century,  the 
eighteenth  century  and  the  Victorian  Age,  take  their  places. 
Their  attainments  should  never  be  estimated  except  in  re- 
lation to  their  opportunities. 

Ample  materials  are  to  be  found  in  the  "Encyclopaedia 
Britannica"  for  studying  the  history  of  science.  We  have 
space  only  to  ask  what  is  the  most  impressive  burthen  of 
such  study.  The  great  gain  which  the  ages  have  brought  to 
science  is  the  increasing  purity  of  aim  of  its  votaries. 
Formerly  knowledge  was  a  means  to  a  practical  end.  Now 
it  is  an  end  in  itself.  To  take  a  simple  illustration  from 
the  history  of  chemistry :  The  ancients  were  acquainted 
with  a  certain  number  of  substances,  some  of  which  when 
placed  in  water  passed  into  solution;  some  when  ignited 
disappeared  in  flame  ;  some  when  heated  with  charcoal  were 
resolved  into  an  earthy  calx  and  a  bright  metal.  They  had 
no  conception  of  the  part  played  by  the  atmosphere  in  com- 
bustion— a  substance  when  burnt  disappeared  in  flame. 
They  had  no  clear  notion  of  the  nature  of  a  compound  — 
matter  when  combined  with  other  matter  was  transmuted 
into  new  matter,  a  change  in  its  nature  was  marked  by  a 
change  in  appearance  and  properties.  What  conclusion 
more  rational  than  that  matter  could  be  created  and  de- 
stroyed, that  it  was  protean,  any  substance  being  change- 


52  AN   INTRODUCTION   TO    SCIENCE 

able  into  any  other  substance  by  a  series  of  transitions,  if 
only  the  right  means  were  employed  ?  The  doctrine  of  the 
indestructibility  of  matter  —  essential  as  it  seems  to  us  as  a 
first  principle  of  science  —has  not  been  established  for  much 
more  than  a  century.  Matter  was  a  transitory  phenomenon 
— the  essential  constituents  of  the  universe,  the  "elements," 
were  earth,  fire,  air  and  water.  And  if  matter  was  capable 
of  unlimited  transmutations,  as  it  appeared  to  be,  it  was 
clearly  possible  to  make  out  of  any  given  substance  any 
other  substance,  even  the  most  desirable,  namely,  gold. 
Here  was  an  object  of  research  so  promising  that  it 
overshadowed  all  others.  It  was  impossible  to  think  of 
alchemy  or  chemistry,  as  we  now  call  it,  without  bearing 
the  possibility  of  this  great  discovery  in  mind.  "Pure" 
chemistry  is  a  growth  of  the  last  hundred  and  fifty  years. 

We  are  apt  to  smile  at  the  delusions  of  the  alchemist. 
His  expectation  that  at  any  moment  he  might  find  gold 
in  his  crucible  seems  to  us  a  "fixed  idea."  But  what  other 
motive  had  he  for  research?  Merely  to  mix  things  to- 
gether, to  heat  them  and  cool  them,  to  sublime  and  con- 
dense, to  dissolve  in  water  or  alcohol,  in  order  that  he 
might  see  what  happened,  was  to  play  the  child.  Anything 
might  happen.  The  result  might  be  pretty  or  ugly,  pleasant 
to  smell,  or  the  reverse ;  but  it  could  not  be  useful.  What 
purpose  was  served  when,  at  the  end  of  a  long  succession 
of  processes,  his  chemicals  disappeared  into  thin  air,  with 
an  unseemly  haste  perhaps  which  smashed  his  retorts  and 
laid  the  philosopher  upon  his  back  ?  Nothing  is  more 
difficult  than  to  transport  oneself  back  into  a  former  age, 
without  carrying  thither  the  mental  preoccupations  of  the 
age  in  which  one  lives.  Had  we  lived  at  the  beginning 
of  the  last  century  what  discoveries  we  should  have  made ! 
No  doubt.  But  what  principle  would  have  guided  our 
researches  before  the  permanence  and  irreducibility  of  the 
elements  as  we  now  know  them  was  established?  To  pass 
matter  through  one  form  after  another  was  futile,  unless  it 


FRANCIS  BACON,  LORD  VERULAM. 
1561  -  1626. 


CLASSIFICATION  53 

had  a  practical  object ;  whereas  to  combine  elements  of 
known  valency  is  to  work  out  a  problem  in  solid  mathe- 
matics. It  can  be  done  on  paper  before  it  is  done  in  the 
laboratory. 

Another  object  for  chemical  research  presented  itself  to 
the  natural  philosopher,  who  was  also  a  physican,  as  the 
most  legitimate  outcome  of  the  theories  of  his  day.  The 
human  body,  which  seemed  to  be  a  properly  constructed 
machine  with  an  innate  tendency  towards  health,  was  never- 
theless constantly  deviating  towards  dyspepsias,  rheums, 
fevers.  What  cause  for  these  aberrations  could  there  be 
save  something  wanting  in  its  chemical  constitution  ?  The 
alchemists  gave  place  to  the  iatro-chemists,  whose  quest 
was  not  gold  but  the  elixir  vitae. 

Scientific  Method.— A  "control-experiment"  is  the 
compass  of  Science.  As  the  mariner  checks  the  course  of 
his  ship  by  comparing  it  with  the  magnetic  meridian,  so 
the  man  of  science  estimates  the  bearings  of  his  observa- 
tions by  comparing  them  with  the  negative  position  — the 
zero-line  from  which  they  diverge.  It  may  be  easy  to 
devise  a  control  experiment,  or  it  may  be  the  crux  of  the 
problem.  When  a  farmer  is  persuaded  by  the  agent  for  a 
manure  company  that  "there  is  nothing  like  kainit  for 
clover,"  he  scatters  it  broadcast  over  his  fields  and  then, 
as  the  crop  grows,  asserts  that  it  is  heavier  or  not  heavier 
than  it  would  have  been  had  no  kainit  been  used.  Probably 
his  judgment  varies  according  as  he  is  a  "go-a-head  man  " 
or  "  one  of  the  old  school,  who  doesn't  hold  with  artificials." 
The  scientific  agriculturist,  on  the  other  hand,  divides  his 
fields  into  sections,  and  sets  aside  in  each  a  control-plot  on 
to  which  no  manure  is  cast.  The  weight  of  clover  obtained 
from  the  "control"  is  compared  with  the  weight  obtained 
from  the  manured  ground.  The  cost  of  the  manure  is 
deducted  from  the  increment  in  value  of  the  crop,  and  the 
difference  is  the  profit  which  accrues  from  the  use  of  the 
manure.  So  far  no  difficulty  in  checking  results  has  been 


54  AN   INTRODUCTION   TO    SCIENCE 

experienced.  But  how  is  he  to  tell  what  the  result  would 
have  been  had  the  season  been  wet  instead  of  dry,  or  dry 
instead  of  wet ;  had  there  been  less  reserve  of  nitrogen  in 
the  soil  or  more  phosphate?  Or,  again,  how  is  he  to  tell 
whether  kainit  is  equally  useful  for  light  soils  and  heavy,  for 
gravels  and  marls  and  clay?  It  is  not  the  experiments  which 
cost  trouble  but  the  control.  Anyone  can  say  try  x,  or  y,  or 
z  ;  it  is  only  the  trained  experimenter  who  can  say  whether 
and  how  far  the  result  is  due  to  the  use  of  x,  or  y,  or  z. 

If,  on  the  map  of  a  certain  country  —  we  are  citing  an 
observation  recently  brought  to  our  notice — the  extent  to 
which  cancer  is  prevalent  is  marked  by  shades  of  grey,  the 
"cancer  spots"  are  sufficiently  dark  to  attract  anyone's 
attention.  Such  a  map  having  been  made,  coincident  con- 
ditions were  sought  for,  and  it  was  observed  that  within 
a  certain  area  wherever  these  foci  of  the  disease  occur  a 
particular  kind  of  tree  (we  will  not  say  what  kind  of  tree, 
lest  someone  unversed  in  scientific  method  wage  a  crusade 
against  it)  is  abundant  and  grows  near  the  houses.  Is 
there  any  connection  between  this  tree  and  cancer  ?  Long 
before  the  life  history  of  "rust"  had  been  worked  out, 
farmers  held  a  conviction  —  it  was  regarded  as  a  vulgar 
prejudice  —  that  their  wheat  was  affected  with  rust  in  fields 
bounded  by  hedges  in  which  the  common  barberry  grew. 
It  has  since  been  ascertained  that  the  fungus  which  in  one 
stage  of  its  existence  affects  wheat  with  rust  is  in  another 
stage  the  aecidium  or  cluster-cup  fungus  of  barberry  ;  and 
it  has  been  found  not  only  that  rust  occurs  where  there  are 
barberries,  but  that  it  does  not  occur  to  the  same  extent 
where  there  are  none.  The  illustration  is  not  altogether 
satisfactory,  for  rust  occurs  in  generation  after  generation 
of  wheat-plants  in  Australia  and  India,  where  the  barberry 
is  not  a  native  plant ;  but  this  fact  does  not  disprove 
Du  Bary's  assertion  that  in  England  its  choice  of  host-plants 
alternates  between  wheat  and  barberry.  It  shows,  however, 
either  that  rust  can  dispense  for  a  long  period  with  the 


CLASSIFICATION  55 

aecidium-stage,  and  that  its  spores,  lying  hid  in  the  grains  of 
corn,  germinate  when  the  wheat  germinates  and  infect  the 
new  wheat-plant  with  the  fungus  ;  or  else  that  in  Australia 
and  India  rust  finds  other  hosts  which  serve  its  purpose 
equally  well.  There  are  difficulties  still  to  be  cleared  up 
regarding  the  mode  of  infection  of  the  corn.  If  our  subject 
were  the  botany  of  parasitic  fungi  we  should  have  to  look 
further  into  the  matter,  but  as  an  illustration  of  the  relation 
which  has  been  supposed  to  exist  between  the  germs  of 
cancer  in  Man  and  their  life  in  a  vegetable  host  the  analogy 
is  sufficiently  complete.  Can  we  say  of  cancer  that  it  does 
not  occur  where  the  suspected  tree  is  absent?  On  the 
contrary,  cancer  is  found  in  coral  islands  where  the  coca-palm 
is  the  only  tree,  and  on  the  plains  of  North  America,  where 
no  tree  raises  its  trunk  for  more  than  a  thousand  miles.  In 
other  districts  other  conditions  have  been  found  associated 
with  great  prevalence  of  cancer  ;  but  as  yet  none  have  stood 
the  test  of  the  control  experiment.  At  present,  therefore, 
the  concurrence  of  the  tree  and  cancer,  like  the  concurrence 
of  various  other  conditions  and  this  fell  disease,  must  be 
looked  upon  as  a  coincidence. 

The  control- observation  is  the  key  to  the  position.  Para- 
doxical as  it  sounds,  the  ingenuity  of  the  man  of  science  is 
taxed  not  in  making  observations  and  devising  experiments, 
but  in  planning  how  to  unmake  them.  The  real  difficulty  is 
not  experienced  in  imagining  a  possible  cause  for  a  known 
effect,  but  in  devising  an  observation  in  which  the  supposed 
predisposing  condition  is  absent,  while  all  other  conditions 
remain  the  same.  The  animal-magnetisers  of  fifty  years  ago 
asserted  that  their  subjects  were  attracted  by  certain  metals 
and  repelled  by  others.  Braid,  to  whose  scientific  investiga- 
tion of  the  phenomena  of  hypnotism  we  owe  the  dissipation 
of  numerous  errors,  when  attending  one  of  their  seances, 
asserted  with  the  same  confidence,  in  the  presence  of  the 
hypnotised  person,  that  he  would  clutch  at  a  round  object 
and  shrink  from  a  pointed  one.  When  he  offered  him  the 


56  AN   INTRODUCTION    TO    SCIENCE 

only  convenient  object  which  he  had  at  hand,  his  latch-key, 
his  prediction  was  verified.  Inverting  the  order  of  his  pre- 
diction on  another  occasion,  it  was  still  verified.  The  cause 
of  the  subject's  movements  lay  not  in  the  thing  presented, 
but  in  the  authoritative  suggestion  that  he  would  behave 
towards  it  in  a  certain  way.  Countless  claims  made  by 
mesmerisers  and  spiritualistic  and  theosophical  miracle- 
workers  of  all  grades  would  fall  to  the  ground  if  their 
audiences  understood  how  to  devise  control-experiments. 
We  have  a  vivid  recollection  of  the  discomforture  cf  a 
certain  "professor"  whose  subject  could  read  the  Lord's 
Prayer  from  a  microscopic  photograph,  could  obey  the 
injunctions  of  his  hypnotist  when  in  a  separate  room,  and 
do  many  other  marvellous  things  when  a  small  scientific 
committee  eliminated  the  possibility  of  suggestion.  The 
droll  feature  of  the  performance  was  the  surprise  of  the 
"professor,"  who  had  deceived  himself.  He  had  taken  for 
granted  that  the  effects  were  caused  by  the  conditions  of 
which  he  made  parade,  and  not  by  other  conditions  which 
he  had  overlooked. 

Scientific  men  are  incessantly  engaged  in  testing  hypoth- 
eses by  eliminating  the  condition  which,  ex  hypothesi,  is 
supposed  to  be  the  cause  of  phenomena.  Science  marches 
by  observing,  by  colligating  observations,  by  speculating  as 
to  the  common  cause  which  results  in  the  similarity  of  the 
phenomena  observed.  We  often  speak  of  the  ingenuity  of 
an  hypothesis,  but  truly  this  is  almost  equivalent  to  assert- 
ing its  falsity  or  its  unnecessary  complication  and  want  of 
finality,  if  it  be  not  false.  The  progress  of  theory  is  towards 
unification,  and  therefore  towards  simplicity.  When,  in 
1859,  Darwin  published  his  doctrine  of  Natural  Selection, 
although  he  saw  that  only  the  fittest  can  survive,  and  that 
the  struggle  for  existence  must  inevitably  eliminate  the  unfit, 
he  did  not  realize  that  this  simple  theory  would  suffice  to 
explain  all  the  adaptations  to  their  environment  presented 
by  all  living  things.  The  eyes  in  a  peacock's  tail  seemed  to 


CLASSIFICATION  57 

Darwin  too  elaborate  to  be  merely  useful ;  they  possessed  a 
quality  in  excess  of  utility,  a  quality  which  affects  us  with 
a  pleasurable  emotion,  and  which  we  therefore  term  beauty. 
Why  should  not  the  pea-hen  be  susceptible  to  the  same 
emotion  ?  It  might  be  that  the  brilliant  colouring  or  bizarre 
marking  of  the  male  was  useful  to  the  female  at  the  breed- 
ing season,  because  it  made  her  mate  more  conspicuous, 
and  so  diverted  the  enemy's  attention  from  her,  or  it  made 
him  more  terrifying  and  therefore  more  useful  as  her  pro- 
tector, but  still  in  selecting  her  mate  she  would  choose  the 
one  which  in  her  eyes  was  the  more  beautiful — does  not  the 
peacock  take  endless  pains  to  display  his  charms? — and 
thus  the  decorations  which  were  in  excess  of  utility  would 
be  perpetuated  and  still  further  developed,  because  the 
female  has  this  sentiment  of  beauty  which  is,  as  it  were,  an 
exaggeration  of  the  sense  of  utility.  Therefore  Darwin 
complicated  his  theory  with  the  doctrine  of  Sexual  Selec- 
tion. Control-observations,  by  eliminating  this  supposed 
cause — the  female's  asthetic  preference— have  shown  that 
the  doctrine  of  Natural  Selection  does  not  need  qualifica- 
tion. Nature  destroys  the  less  fit.  In  peacocks,  fitness  is 
proportional  to  gorgeousness. 

One  more  illustration  of  a  control-observation  of  an 
entirely  different  class.  When  a  group  of  natural  phe- 
nomena are  observed,  and  an  explanation  of  the  feature 
which  they  present  in  common  is  formulated,  the  theorist 
asks  himself,  "Can  I  find  the  same  result  in  the  absence  of 
any  supposed  cause  ?  Can  I  find  the  same  cause  at  work 
without  the  same  result  ensuing?"  Then  he  arranges  his 
conditions  artificially  —  makes  an  experiment,  that  is  to  say 
— and  obtains  a  certain  result.  The  next  step  is  to  omit  the 
condition  which  he  believes  to  be  the  cause  of  the  result, 
and  to  see  if  the  result  is  the  same.  Sometimes,  on  the 
other  hand,  it  is  not  the  facts  that  he  needs  to  test,  but  his 
own  attitude  of  mind  towards  the  facts.  It  is  not  uncom- 
mon to  hear  the  remark,  even  in  semi-cultured  society, 


58  AN    INTRODUCTION    TO   SCIENCE 

"The  moon  changes  to-night;  we  shall  have  a  change  in 
weather."  "How  often  does  your  moon  change,  dear 
madam?"  asks  the  man  of  science.  "Once  a  week,  of 
course."  "Well,  you  see  I  have  adopted  the  metric 
system.  My  moon  changes  ten  times  in  a  month,  and 
therefore,  as  this  is  just  the  end  of  the  first  week,  my 
weather  can't  change  for  at  least  another  day." 

How  are  we  to  know  that  phenomena  which  appear  to  be 
alike  are  alike  in  quality,  and  not  merely  alike  in  appear- 
ance, or,  in  other  words,  how  can  we  tell  that  the  fact  that 
they  are  alike  indicates  that  their  likeness  is  due  to  the  same 
cause  ?  Fifteen  years  ago,  when  Dr.  Gaskell  announced  his 
theory  of  the  origin  of  Vertebrates  from  a  crustacean-like 
ancestor,  with  the  amazing  inferences  as  to  changes  in  the 
functions  of  organs  which  such  a  hypothesis  implies,  I  hap- 
pened to  visit  one  of  the  most  eminent  of  living  zoologists, 
to  whom  I  expounded  the  evidence  upon  which  the  theory 
was  based.  "  Gaskell  has  a  fiendish  ingenuity  in  collecting 
coincidences,"  was  the  professor's  comment.  But  what 
higher  praise  can  be  bestowed  upon  any  observer?  It  is  his 
business  to  collect  coincidences,  and  then  to  postulate  the 
cause  which  determines  that  the  observed  phenomena  coin- 
cide. When  he  has  found  this,  he  is  in  a  position  to 
formulate  a  "law."  Yet  anyone  who  pays  attention  to  this 
matter  will  learn  that  it  is  very  dangerous  to  conclude  that 
because  things  coincide  therefore  they  have  a  common 
cause.  It  is  mathematically  expressed  in  the  Law  of 
Chance,  and  yet  in  everyone's  experience  there  has  hap- 
pened at  some  time  or  other  so  startling  a  coincidence  that 
no  Law  of  Chance  seems  adequate  to  account  for  it.  Here 
is  one  which  could  hardly  be  devised  in  the  fertile  brain  of 
a  Sherlock  Holmes.  The  present  President  of  the  Royal 
College  of  Surgeons  of  Edinburgh  told  the  writer  that  some 
time  ago  a  woman  was  brought  into  his  ward  in  the  In- 
firmary at  Edinburgh  shot  in  the  breast  by  a  bullet  from  a 
revolver  which  some  one  was  examining  in  a  pawn-shop. 


CLASSIFICATION  59 

The  woman  recovered.  Nine  years  afterward  a  boy  was 
brought  into  his  ward  shot  in  the  chest  by  a  bullet  from  a 
revolver  which  some  one  was  examining  in  a  pawn-shop. 
The  boy  died,  and  an  inquest  was  held.  Some  days  after 
the  inquest  the  chief  of  police  entered  Dr.  Chiene's  con- 
sulting room,  and,  producing  a  revolver,  said,  "I  have  some- 
thing here  that  will  interest  you.  You  said  at  the  inquest 
that  it  was  a  very  remarkable  coincidence  that  you  should 
twice  have  had  in  your  ward  a  person  shot  in  such  an  un- 
likely way.  I  have  looked  up  the  old  case,  and  I  find  that 
this  pistol  which  killed  the  boy  is  the  same  one  which  shot 
the  woman."  Anyone  with  a  touch  of  superstition  would 
be  likely  to  remark  that,  until  that  pistol  has  been  dropped 
into  the  deepest  hole  in  the  Pacific  Ocean,  it  is  not  safe  to 
enter  a  pawnshop ! 

From  the  infinite  sum  of  our  fancies  and  illusions  par- 
ticular instances  are  picked  out  upon  which  are  based  mar- 
vellous tales  of  telepathic  communication  and  premonition 
in  dreams.  If  they  were  not  marvellous  they  would  not  be 
remembered,  and  if  their  marvellousness  hardly  merits  the 
telling,  a  tendency  is  innate  in  most  narrators  to  bring  it  up 
to  the  effective  standard.  Such  stories  as  have  been  pub- 
lished are  conspicuously  wanting  in  the  only  kind  of  sup- 
port which  would  give  them  value  as  evidence  —  documen. 
tary  corroboration.  Does  any  residium  which  cannot  be 
explained  without  the  inference  of  the  existence  of 
"psychic  force"  remain  over  after  coincidence  and  un- 
conscious and  conscious  lying  have  been  allowed  for  ?  We 
think  not. 

Has  science  a  method  proper  to  itself?  Induction  and 
deduction  are  terms  which  sound  antithetical.  They  have 
been  the  watchwords  of  opposing  forces  in  many  a  battle. 
For  more  than  a  century  thinking  Europe  was  divided  into 
Baconians  and  Cartesians.  Francis  Bacon  laid  down  the 
laws  of  scientific  evidence  in  his  novum  organum  with 
much  the  same  pedantry  as  he  would  have  displayed  in 


60  AN   INTRODUCTION    TO    SCIENCE 

regulating  judicial  procedure.  "He  talks  as  a  Lord 
Chancellor,"  said  Hobbes.  According  to  Lord  Chancellor 
Verulam,  Science  must  progress  from  step  to  step,  never 
committing  itself  to  any  hypothesis  which  is  not  the  nec- 
essary inference  from  observation.  The  true  scientific 
method  is  always  to  be  strictly  inductive — a  most  useful 
restriction,  and  especially  necessary  in  Bacon's  day. 

Descartes'  richer  imagination  took  longer  flights.  In 
certain  matters  he  even  asked  of  his  inner  consciousness 
how  he  himself  felt  that  things  ought  to  be?  How  would 
he  have  made  them  had  he  had  the  making  of  the  world  ? 
Then  he  collected  evidence  to  show  that  they  are  as  he 
supposed  ti  priori  that  they  would  be.  This  is  deduction ; 
building  downwards,  although  the  process  by  which  Des- 
cartes tested  his  evidence  was  as  strictly  inductive  as 
Bacon  could  exact. 

After  all,  the  difference  between  induction  and  deduction 
is  a  question  of  name.  We  know  nothing  of  the  universe 
but  that  which  we  have  learnt  by  experience  or  that  which 
our  predecessors  have  learnt  by  experience  and  have  re- 
corded for  us.  ,  \Vhen  the  imagination  takes  a  long  flight, 
when  it  seeks  an  a  priori  explanation,  it  is  but  appealing 
to  experience,  although  it  is  unable  to  trace  the  steps 
along*  which  the  reason  marches  in  seeking  so  distant  a 
cause  for  effects  which  are  near  at  hand.  And  \vhen  we 
come  back  to  experience  for  proof  of  the  applicability  of 
far-fetched  explanations  the  reason  moves  towards  it  by 
processes  of  induction.  Every  hypothesis  is  by  definition 
an  advance  on  knowledge.  It  is  in  the  nature  of  a  deduc- 
tion that  reason  goes  on  before  observation.  Observations 
are  then  built  up  to  support  reason.  The  difference  between 
induction  and  deduction  is  but  a  difference  in  degree. 

It  is  characteristic  of  science  to  proceed  with  the  utmost 
caution  to  build  a  pyramid  of  inductions,  each  tier  of 
which  contains  a  smaller  number  of  generalisations  than 
the  tier  upon  which  it  rests,  until  the  apex  is  a  compre- 


CLASSIFICATION  61 

hensive  generalisation  which  unifies  all  below  it.  Specu- 
lation is  the  scaffolding  or  system  of  guiding  lines  of  this 
edifice.  As  facts  are  packed  beneath  it  the  apex  of  the 
scaffolding  has  to  be  shifted,  raised,  lowered,  until  at  last 
it  is  properly  centred.  Then  the  whole  is  so  compact 
that  no  fact  can  be  detached. 

Darwin  abolished  the  distinction  between  induction  and 
deduction  in  science.  His  hypothesis  was  of  so  general  a 
character  that  it  embraced  every  manifestation  of  life ;  it 
gave  a  reason  for  the  form  and  functions  of  every  organ 
of  every  living  thing.  The  history  of  philosophy  cannot 
give  an  instance  of  a  wider  generalisation,  and  yet  the 
proofs  of  Darwin's  hypothesis,  which  far  outstretched  Des- 
cartes' most  imaginative  deduction,  are  as  rigidly  induc- 
tive as  Bacon  could  desire. 


LORD  KELVIN,  late  P.  R.  S 


SECTION    II 

CHAPTER   III 
The  Age  of  the  Earth 

FEW  subjects  of  research  and  speculation  are  more  inter- 
esting than  this.  An  attempt  to  ascertain  the  age  of  the 
earth,  or  rather  to  ascertain  the  length  of  time  during  which 
the  earth  has  been  such  as  we  now  know  it — a  solid  globe 
capable  of  supporting  life — brings  us  face  to  face  with  far- 
reaching  questions  which  cannot  fail  to  impress  the  imagi- 
nation. Although  the  solution  of  these  questions  will  never 
influence  the  use  which  each  individual  makes  of  his  own 
life,  they  nevertheless  appear  to  be  of  fundamental  impor- 
tance to  every  one  who  seeks  to  bring  the  universe  within 
his  mental  grasp.  The  attempt  to  give  a  general  idea  of  the 
data  which  are  available  will  afford  us  the  opportunity  of 
illustrating  the  methods  adopted  by  astronomers,  physicists, 
geologists  and  biologists  in  grappling  with  the  problem. 

For  how  long  have  the  conditions  upon  the  surface  of  the 
earth  been  such  as  to  render  Life  possible?  By  life  we 
mean  the  existence  of  such  organisms  as  now  surround  us — 
organisms  which  depend  upon  the  possession  of  a  nitroge- 
nous compound,  protoplasm,  for  the  chemical  changes  by 
which  the  phenomena  of  living  are  exhibited  ;  and  upon 
the  presence  in  the  atmosphere,  or  dissolved  in  water,  of  the 
element  oxygen  with  which  their  nitrogenous  constituents 
may  combine.  We  cannot  imagine  any  other  kind  of  life. 

1&3) 


64  AN   INTRODUCTION    TO    SCIENCE 

If,  when  we  ask  the  inevitable  question,  "Is  this  the  only 
planet  upon  which  life  is  possible?"  the  astronomer  or 
spectroscopist  answers,  ' '  There  is  no  other  in  which  proto- 
plasm would  remain  a  compound,  or  in  which  it  would  find 
itself  in  the  presence  of  oxygen  ;"  then  it  is  idle  to  speculate 
as  to  whether  life  is  possible  elsewhere  than  on  the  earth.  If 
Venus  does  not  rotate  upon  her  axis,  but  always  turns  one 
face  to  the  sun  and  the  other  to  the  outer  cold,  there  is  no 
life  on  Venus.  If  Mars  is  too  cold  for  protoplasmic  meta- 
bolism, or  if,  as  Dr.  Johnstone  Stoney  calculates,  the  force 
of  gravity  on  this  planet  is  too  small  to  prevent  water- 
vapour  from  escaping  into  space,  then  there  is  no  life  on  Mars. 
Speculation  as  to  the  possible  existence  of  different  orders 
of  living  things,  of  beings  which  do  not  contain  nitrogen  or 
exhibit  life  by  combining  with  oxygen,  pierces  beyond  the 
domain  of  science.  There  have  not  been  wanting  thinkers 
who  assert  that  they  can  imagine  beings  in  whose  constitu- 
tion silicon  plays  the  same  part  which  nitrogen  plays  i:i 
ours  ;  living  things  with  the  same  constitution  as  china  dolls. 
Fancy  may  play  at  speculation  in  this  way.  It  may  surround 
its  new  creation  with  an  atmosphere  of  iodine,  and  feed 
its  inhabitants  upon  carbonate  of  lime.  They  may  suffer 
calcareous  pains  and  give  way  to  siliceous  emotions. 
But  it  is  not  Science.  Speculation  has  lost  touch  with 
experience. 

Living  things  require  certain  strictly  limited  conditions  of 
existence.  Plants  cannot  fix  carbon  from  the  atmosphere 
unless  the  temperature  be  somewhat  above  the  freezing 
point,  and  somewhat  less  than  half-way  to  the  boiling  point 
of  water ;  and  animal  life  depends  upon  the  preexistence 
of  plants.  The  question  is  therefore  narrowed  down  to 
this  :  For  how  long  has  the  temperature  of  the  earth  been 
fixed  within  these  limits,  other  conditions,  such  as  the  force 
of  gravitation  and  the  receipt  of  light  from  the  sun,  being 
the  same  as  at  present?  Sunshine  and  shower,  day  and 
night,  moderate  heat  and  moderate  cold  were  as  necessary 


THE    AGE    OF    THE    EARTH  65 

to  the  first  inhabitants  of  the  globe  as  they  are  to  the  plants 
and  animals  which  live  upon  it  now. 

The  answer  to  this  question  hardly  comes  within  the 
province  of  the  astronomers.  Yet  they  were  the  first  to 
show  that  there  is  evidence  of  such  a  change  in  the  move- 
ments of  the  earth  as  must,  when  traced  backwards,  bring 
us  at  last  to  a  far  limit  for  its  inhabitableness.  Astronomi- 
cal observations  prove  that  the  rapidity  with  which  the 
earth  rotates  has  sevsibly  diminished  within  historic  times. 
Laplace  showed  that  the  relative  velocity  of  the  rotation  of 
the  earth  and  of  the  orbit  of  the  moon  have  changed.  The 
time  of  commencement  of  eclipses  of  the  moon,  the  time, 
that  is  to  say,  after  the  moon  had  risen  before  the  eclipse 
commenced,  and  of  their  duration,  have  been  recorded  with 
accuracy  since  they  were  noted  by  the  astronomers  of  Baby- 
lon twenty-seven  centuries  ago,  and  from  these  records  it  is 
clear  that  either  the  rate  at  which  the  moon  travels  has 
increased  or  the  rapidity  of  the  earth's  rotation  has  steadily 
diminished.  Laplace  considered  that  the  moon  has  hurried 
while  the  earth  has  kept  time,  and  he  pointed  out  a  cer- 
tain cause  (the  progressive  diminution  of  the  excentricity  of 
the  earth's  orbit)  which  must  produce  an  acceleration  of  the 
moon's  motion  ;  but  Adams,  after  estimating  the  utmost 
effect  of  this  accelerating  cause,  found  that  it  can  only  ac- 
count for  one-half  of  the  discrepancy  in  time  between  the 
moon  and  the  earth.  It  is  indisputably  true  that  the  earth 
is  losing  its  velocity  of  rotation.  It  is  twenty-two  seconds 
later  at  the  end  of  every  century.  Every  day  is  therefore 
longer  by  the  fraction  of  a  second  than  the  corresponding 
day  of  the  year  before. 

F,or  this  loss  of  time  on  the  earth's  part  the  moon  is 
chiefly  responsible,  since  the  attraction  of  the  moon  is  the 
main  factor  in  producing  tides,  and  the  slowing  of  the 
earth  is  due  to  the  friction  of  its  envelope  of  water.  As 
the  earth  rotates  it  tends  to  leave  its;  envelopes  of  water 
and  air  behind  it,  because  the  attraction  of  the  moon  and 


66  AN    INTRODUCTION    TO    SCIENCE 

the  sun  keep,  as  it  were,  a  hold  upon  them.  The  heaping 
up  of  the  tide  is  not  merely  a  rising  of  the  water  towards 
the  moon,  but  the  wave  is  drawn  backwards  with  regard 
to  the  movement  of  the  earth.  Now,  wherever  there  is 
movement  of  matter  upon  matter,  whether  the  substances 
rubbed  against  one  another  be  solid,  liquid  or  gaseous, 
energy  is  liberated.  This  energy  takes  the  form  of  heat, 
which  is  dissipated  into  space,  unless  there  be  some  coun- 
tervailing conditions  which  restore  the  heat  to  the  body 
losing  it.  The  friction  of  the  tidal  wave  upon  the  surface 
of  the  earth  diminishes  the  energy  of  the  earth's  rotation  in 
exactly  the  same  manner  as  a  brake  diminishes  the  energy 
of  rotation  of  a  wheel.  In  point  of  fact,  the  moon  puts  a 
continuous  brake  upon  the  earth. 

There  is,  therefore,  no  reason  to  call  in  question  the  ac- 
curacy of  the  records  of  eclipses  of  the  moon.  They  supply 
historical  evidence  that  the  earth  rotated  more  rapidly  in 
former  times  than  it  does  now.  If  we  had  no  such  records 
we  should  still  be  able  to  prove  that  the  friction  of  the 
tides  must  have  produced  a  slowing  effect. 

The  evidence  as  to  the  actual  rate  of  rotation  can  be  put 
to  a  most  important  use.  We  know  that  once  this  earth 
was  so  hot  that  it  was  molten.  Now,  when  a  fluid  sphere 
is  made  to  rotate  the  centrifugal  force  at  its  equator  increases, 
while  the  polar  diameter  is  diminished,  and  the  extent  to 
which  it  assumes  the  form  of  a  disc  with  a  rounded  edge 
(an  oblate  spheroid)  depends  upon  the  amount  of  the  cen- 
trifugal force,  i.e.,  upon  the  velocity  of  its  rotation.  The 
earth,  as  we  know  it,  is  almost  perfectly  rigid.  We  still 
speak  of  the  "crust  of  the  earth "  as  if  its  surface  only  were 
solid  and  its  contents  molten,  but  this  theory  has  been 
abandoned.  Physicists  hold  now  that  the  earth  is  solid  to 
its  core,  except  for  patches  of  molten  lava.  At  any  rate,  it 
is  so  nearly  rigid  that  any  deformation  by  centrifugal  force 
or  return  towards  sphericity  owing  to  the  diminution  of  cen- 
trifugal force,  is  out  of  the  question.  The  earth  has  the 


THE    AGE  OF    THE    EARTH  67 

shape  which  it  assumed  when  it  first  became  cool  enough 
to  solidify.  It  is,  as  we  have  said,  an  oblate  spheroid,  but 
the  difference  in  length  between  the  axis  joining  the  poles 
and  the  axis  passing  from  one  side  of  the  equator  to  the 
other  is  much  smaller  than  the  contemplation  of  most  models 
of  the  globe  would  lead  one  to  suppose.  The  equatorial 
axis  is  only  seventeen  miles  longer  than  the  polar  axis. 
Therefore  it  cannot  have  been  spinning  much  faster  when 
it  first  became  solid  than  it  does  now.  Lord  Kelvin  esti- 
mates that  the  centrifugal  force  at  the  time  of  solidification 
cannot  have  been  more  than  3  per  cent  greater  than  it  is 
at  .present,  and  therefore,  having  regard  to  the  known  rate 
of  retardation  of  the  earth's  rotation,  this  event  occurred 
not  more  than  100  million  years  ago. 

Another  line  of  argument  which  leads  to  much  the  same 
result  depends  upon  the  evidence  that  the  earth  is  losing 
heat.  The  craters  of  extinct  volcanoes,  scattered  over  all 
parts  of  the  globe,  testify  to  the  existence  of  much  greater 
plutonic  activity  in  former  times  than  is  anywhere  exhibited 
now.  The  sixty  or  more  cones  which  may  be  seen  from  the 
top  of  Mount  Eden,  in  the  neighbourhood  of  Auckland,  New 
Zealand,  give  to  the  landscape  the  appearance  which  the 
surface  of  the  moon  would  present  were  it  clothed  in  green, 
and  the  almost  perfect  preservation  of  the  cups  of  Mount 
Eden  itself  and  of  some  of  the  surrounding  volcanoes  shows 
that  it  cannot  be  very  long,  in  geological  time,  since  they 
were  in  action.  The  subsidence  of  volcanic  activity  proves 
that  there  is  less  heat  than  formerly  beneath  the  surface  of 
the  earth. 

Again,  it  can  be  shown  that  the  nature  of  the  record,  pre- 
served in  this  case  by  the  rocks,  might  have  been  antici- 
pated by  a  process  of  reasoning.  It  has  long  been  known 
that  the  heat  of  the  earth  is  greater  at  the  bottom  of  r  a 
mine  than  it  is  near  the  surface.  Observations  made  in  many 
regions  show  that,  after  a  level  down  to  which  the  temper1 
ature  is  affected  by  the  heat  of  summer  and  the  cold  of 


68  AN   INTRODUCTION    TO    SCIENCE 

winter — a  depth  of  a  few  feet  only  in  England — the  tem- 
perature steadily  rises  to  the  extent  of  i°  F.  for  every  50  or 
60  feet.  This  proves  that  the  more  superficial  strata  are 
losing  heat  which  they  receive  by  conduction  from  strata 
placed  more  deeply.  The  earth  is  shedding  heat  into  space. 
Lord  Kelvin  has  calculated  the  amount  of  heat  which  is 
dissipated  yearly,  and  has  estimated  the  time  which  has 
elapsed  since  the  surface  of  the  earth  was  so  hot  that  all 
water  upon  it  must  have  been  in  the  form  of  steam.  This, 
he  says,  was  the  condition  of  the  globe  less  than  100  million 
years  ago. 

Lastly,  the  physicist  attacks  the  problem  from  quite  a 
different  side.  Having  determined  the  outside  limit  of  the 
age  of  the  earth,  he  turns  to  the  sun  and  asks,  How  old  is 
that  ?  How  long  has  the  sun  been  pouring  forth  the  force 
which  keeps  plants  and  animals  alive  ?  What  is  the  source 
of  his  energy  ?  It  cannot  come  from  the  same  source  from 
which  we  commonly  obtain  it,  combustion.  Had  the  whole 
sun  been  made  of  coal  with  an  infinite  atmosphere  of  oxy- 
gen in  which  to  burn,  it  would  have  gone  out  in  a  few 
thousand  years.  When  this  fact  was  recognized  it  was  sug- 
gested that  the  great  mass  of  the  sun  might  attract  me- 
teors, fragments  of  broken-up  worlds,  which  would  rush 
towards  it  with  such  velocity  as  to  set  free,  when  they  struck 
it,  the  energy  which  the  sun  disperses  as  heat.  But  for  the 
supply  of  the  sun's  heat  in  this  way  meteors  equal  in  size, 
in  the  aggregate,  to  the  moon  would  need  to  be  sacrificed 
every  year,  and  astronomy  proves  that  space  is  not  pervaded 
by  such  a  multitude  of  shooting  stars.  It  is  now  agreed  that 
the  heat  of  the  sun  is  produced  by  the  collision  of  the  parti- 
cles of  matter  of  which  it  is  itself  composed.  These  collisions 
are  brought  about  by  the  shrinking  of  the  sun,  which  is 
losing  four  miles  in  diameter  every  century.  To  the  ques- 
tion, how  long  has  the  emission  of  heat  by  this  process 
been  going  on  ?  Lord  Kelvin  answers  :  ' '  The  sun  may 
have  already  illuminated  the  earth  for  as  many  as  100  million 


THE    AGE    OF    THE   EARTH  69 

years,  out  it  is  almost  certain  that  he  has  not  illuminated 
the  earth  for  500  millions  of  years." 

Thus  the  physicists  have  approached  the  problem  from 
several  sides,  and,  drawing  the  mesh  tighter  and  tighter,  have 
shown,  not  how  long  the  earth  has  been  capable  of  support- 
ing life,  but  what  is  the  limit  beyond  which  it  is  certain  that 
it  was  not  so  constituted.  Lord  Kelvin  is  of  opinion  that 
this  limit  does  not  exceed  20  million  years.  Physical  methods 
involve  long  calculations,  and  the  indisputable  accuracy  of 
mathematics  gives  to  the  results  an  appearance  of  rigid 
exactitude  which  may  be  misleading.  It  is,  however,  obvious 
that  mathematics  cannot  produce  an  accurate  result  unless 
the  data  be  accurate,  and  if  there  be  any  uncertainty  in  the 
conclusions  just  formulated,  it  must  be  due  to  errors  in  the 
data  upon  which  they  are  based.  Each  of  the  estimates 
starts  with  certain  assumptions.  We  are  very  far  from 
calling  these  in  question,  but  if  any  person  is  ever  found 
competent  to  act  as  umpire  between  the  physicists  and  the 
geologists  (who,  as  we  shall  show  directly,  prove  a  longer 
period  than  20  millions  of  years),  he  will  inquire  first  whether 
these  assumptions  are  justified.  Is  the  retardation  assigned 
in  right  proportions  to  the  moon  and  the  sun  respectively  ? 
Is  it  true  that  the  shape  of  the  earth  has  not  altered  since  it 
cooled  to  the  point  of  solidification  ?  Do  the  figures  which 
represent  the  increasing  heat  of  the  earth  from  without 
inwards  hold  good  for  all  latitudes,  and  are  they  independent 
of  local  causes,  such  as  the  proximity  of  mountains,  etc.  ? 

Geologists  approach  the  problem  from  the  opposite  side. 
They  ask  the  direct  question,  How  long  has  it  taken  to 
deposit  all  the  fossil-bearing  strata,  and  the  earlier  sedi- 
mentary rocks  which  were  capable  of  supporting  life, 
although  no  fossils  are  preserved  in  them  ?  Sir  Archibald 
Geikie  answers  that  it  must  have  taken  more  than  20 
million  years.  These  strata  attain  in  the  aggregate  to  the 
thickness  of  100,000  feet.  The  chalk  alone  reaches  to  a 
thickness  of  10,000  feet  in  certain  of  the  western  districts  of 


70  AN    INTRODUCTION   TO    SCIENCE 

the  Rocky  Mountains,  and  chalk  is  a  deposit  which  could  be 
formed  but  very  slowly  at  any  period  of  the  earth's  history, 
seeing  that  it  is  made  up  of  the  shells  of  microscopic  animals 
which  obtain  the  carbonate  of  lime  for  the  manufacture  of 
their  testae  from  the  sea.  But,  neglecting  all  details,  and 
looking  at  the  matter  from  the  broadest  point  of  view,  Geikie 
endeavours  to  ascertain  the  rate  at  which  the  materials  which 
form  rocks  are  deposited  ;  and  since  all  these  materials  are 
borne  down  to  the  sea  by  rivers,  we  can  calculate,  if  we  know 
the  amount  which  any  river  carries  down  in  a  year,  the 
depth  to  which  it  will  cover  a  given  area  of  the  bottom  of 
the  sea.  Measurements  which  have  been  made  show  that 
rivers  deposit  from  T^  to  ^Vcr  °f  a  f°ot  *n  a  vear>  over  an  area 
equal  to  the  area  from  which  they  obtained  the  mud,  sand 
and  gravel  which  they  wash  into  the  sea.  The  limits  between 
which  the  deposit  varies  are  necessarily  wide,  because  the 
activity  of  the  process  of  denudation  of  the  land  varies  so 
greatly.  Mountains  are  worn  down  more  rapidly  than  plains, 
and  where  the  rainfall  is  heavy,  or  the  splitting  action  of 
frost  comes  into  play,  denudation  is  much  more  rapid  than 
in  dry,  warm  places.  Supposing  the  area  of  sea  to  have 
been  always  equal  to  the  area  of  land,  and  the  rivers  to  be 
the  only  carriers  of  deposits,  it  is  clear  that  it  would  take 
from  70  to  700  millions  of  years  to  lay  down  strata  100,000 
feet  in  thickness.  These  figures  are  interesting  as  guiding 
lines  of  thought,  but  it  is  obvious  that  corrections  must  be 
made  for  the  carrying  power  of  the  wind,  which  robs  the 
rivers  of  much  of  the  dust  and  sand  which  would  otherwise 
find  their  way  into  their  streams,  and  for  the  eroding  action 
of  the  sea  itself.  Nor  is  it  certain  that  the  aggregate  thickness 
of  the  strata  would  amount  to  100,000  feet  if  it  could  be 
measured  in  any  one  given  place.  Sir  Archibald  Geikie  says 
that  "on  a  reasonable  computation  these  stratified  masses, 
where  most  fully  developed,  attain  a  united  thickness  of  not 
less  than  100,000  feet."  But  it  is  unlikely  that  all  could  have 
been  fully  developed  in  any  one  place,  since  at  no  time  was 


THE    AGE    OF    THE   EARTH  71 

the  same  deposition  occurring  all  over  the  globe.  Where 
one  kind  of  rock  was  formed  for  a  very  long  period  in  one 
place,  so  that  it  attained  to  great  thickness,  the  next  succeed- 
ing stratum  may  in  that  particular  place  have  been  very  thin. 

And  again,  as  pointed  out  by  Mr.  Wallace,*  although  the 
denudation  of  the  land  by  the  agency  of  rain  extends  over 
very  large  areas,  the  rivers  deposit  all  the  silt  which  they 
carry  down  to  the  sea  within  150  miles  from  the  coast,  and 
even  this  limit  is  reached  only  opposite  to  the  mouths  of  large 
rivers.  It  is,  therefore,  necessary  for  the  purpose  of  calcula- 
tion that  an  estimate  should  be  made  of  the  average 
thickness  of  the  sedimentary  rocks  all  over  the  globe,  beneath 
the  bottom  of  the  oceans  as  well  as  over  existing  continents. 
Until  this  has  been  done,  and  at  present  it  seems  to  be  an 
impossible  task,  the  geological  figures  are  of  comparatively- 
little  value. 

To  biologists  this  controversy  is  of  great  interest,  although 
they  cannot  be  said  to  have  any  claim  to  an  independent 
opinion,  since  they  have  absolutely  no  standard  by  which  to 
gauge  evolutionary  time.  Although  plants  and  animals  have 
been  changed  profoundly  by  cultivation  and  breeding  within 
historic  times,  there  is  no  evidence  that  they  have  changed 
within  the  historic  period  without  Man's  interference.  It  is 
impossible  to  prove  that  the  hands  of  the  evolutionary  clock 
have  moved.  Such  negative  evidence  is  of  value,  however, 
as  showing  that  if  evolution  proceeds  so  slowly  that  it  cannot 
be  detected  in  the  process,  even  though  its  records  extend 
over  several  thousands  of  years,  it  must  have  required  a  long 
period  to  allow  of  the  changes  in  the  forms  of  living  things 
which  are  pictured  in  the  fossil-bearing  rocks.  When 
Charles  Darwin  was  submitting  to  the  world  his  doctrine  of 
the  Origin  of  Species,  he  felt  it  necessary  to  insist,  "how 
incomprehensively  vast  have  been  the  past  periods  of  time," 
because  he  foresaw  that  the  objection  would  inevitably  be. 


*  "  Island  Life,"  chap.  x. 


72  AN    INTRODUCTION   TO    SCIENCE 

raised  that  the  world  had  not  existed  long  enough  to  allow  of 
the  origin  of  all  living  forms  by  evolution.  But  although, 
to  put  it  briefly,  the  biologist  wants  as  much  time  as  he  can 
get,  he  has  not  the  least  idea  as  to  how  much  would  suffice. 
An  interesting  side  issue  has  recently  been  raised.  An 
eminent  zoologist  has  expressed  the  opinion  that  evolution  in 
early  times  and  among  primitive  forms  proceeded  more 
rapidly  than  it  has  done  since.  Evidence  bearing  upon  this 
view  is  likely  to  be  sought  for  eagerly  during  the  next  few 
years.  At  first  sight  it  appears  more  likely  that  the  change 
in  the  rapidity  of  evolution  has  been  in  the  opposite  direc- 
tion ;  that  as  competition  has  become  keener  the  extent  of 
variation  has  increased.  Among  simple  and  comparatively 
uniform  organisms  favourable  variations  of  very  small  extent 
would  give  great  advantage  to  their  possessors.  As  speciali- 
zation increases,  a  variation  is  of  little  use  unless  it  is  pro- 
nounced. Just  as,  to  reason  from  analogy,  a  new  sign-board 
sufficed  to  bring  business  to  a  tradesman  two  centuries  ago  ; 
whereas  only  the  boldest  advertisements  attract  attention  at 
the  present  time.  Again,  it  cannot  be  supposed  that  all  the 
surface  of  the  globe  became  life-supporting  at  the  same 
epoch.  As  the  earth  cooled,  the  regions  in  which  living 
things  could  exist  must  have  increased  in  area,  and  although, 
on  account  of  the  rapidity  of  their  multiplication,  this  exten- 
sion of  the  life-carrying  area  may  have  counted  for  very 
little,  it  must,  in  some  degree,  have  delayed  the  crisis  of 
the  struggle  for  existence.  Uniformity  of  reproduction 
would  seem  to  be  the  primitive  law.  It  might  be  supposed 
that  when  the  pendulum  of  variation  first  began  to  swing 
its  excursions  were  almost  imperceptible,  and  that  their 
departures  from  zero  have  been  steadily  increasing  ever 
since.  Indeed,  the  very  tendency  to  vary  is  a  favourable 
variation  in  itself,  which  would  be  steadily  increased  by 
natural  selection,  since  the  race  with  the  greatest  poten- 
tiality of  variation  is  the  most  likely  to  hold  its  own  under 
changed  conditions  of  existence.  On  the  other  hand,  the 


THE   AGE   OF    THE   EARTH  73 

rock-records  seem  to  indicate  either  a  diminishing  range  of 
variation  or  an  increasing  rate  of  deposition.  Either  it  took 
longer  for  the  older  strata  to  accumulate,  or  the  plants  and 
animals  which  are  fossilized  in  them  changed  from  one 
form  into  another  with  greater  rapidity  than  they  did  in 
later  periods  of  geological  time.  Again,  it  might  be  urged 
that  as  specialization  increases  all  the  openings  for  new 
developments  are  filled  up.  With  the  present  almost  infinite 
variety  of  forms  it  is  almost  impossible  for  a  plant  or  an 
animal  to  discover  an  effective  new  departure. 


CHAPTER    IV 
The   Ultimate   Constitution  of  Matter 

IN  chemistry  more  than  in  any  other  branch  of  Natural 
Science  it  is  possible  to  draw  a  marked  distinction  between 
the  work  of  the  laboratory  and  the  work  of  the  study — 
between  manipulation  and  philosophical  thought.  Two 
lines  of  research  stretch  to  the  chemist's  mental  horizon. 
He  may  either  devote  the  chief  part  of  his  time  to  investi- 
gating the  properties  of  substances,  or  he  may  reason  as 
to  the  relation  between  substances  and  their  properties, 
and  devise  experiments  to  check  his  hypotheses.  He  is 
in  charge  of  the  matter  of  the  universe.  It  is,  in  the  first 
place,  his  business  to  prepare  all  the  substances  which 
can  exist  in  a  pure,  homogeneous  or  isolated  stale,  and  to 
investigate  their  behaviour  in  relation  to  one  another.  He 
separates  matter  as  it  is  found  in  nature  into  its  elements. 
He  forms  every  combination  of  the  elements  which  under 
any  conditions  can  exist  as  homogeneous  bodies  —  as 
bodies,  that  is  to  say,  the  properties  of  which  are  invari- 
able and  uniform  throughout  their  whole  mass.  That  the 
substance  with  which  he  is  dealing  is  partially  or  com- 
pletely decomposed  during  many  of  his  manipulations  — 
that,  for  example,  a  salt  when  dissolved  has  not  the  same 
homogeneity  which  it  exhibited  in  its  crystalline  form  before 
he  dropped  it  into  the  water — that  it  is  partially  resolved 
by  the  water  into  its  "ions" — does  not  affect  the  final 
result,  profoundly  as  it  modifies  the  action  of  this  salt 
upon  other  salts  in  the  same  solution.  The  chemist  recog- 

(74) 


THE   HON.  ROBERT  BOYLE. 
1627-1691. 


ULTIMATE   CONSTITUTION    OF    MATTER        75 

nises  that,  when  he  is  working  with  a  substance  in  solution, 
his  homogeneous  or  unit  substance  is  not  the  salt  with  the 
properties  of  which  he  is  conversant  in  its  dry  condition. 
The  salt  tends  to  divide  into  its  ions.  It  is  the  reactions 
of  the  separated  ions  that  he  is  now  investigating,  not  the 
reactions  of  the  salt  as  a  whole.  But  at  the  end  of  the 
reaction  a  new  product  comes  back  into  the  light,  and  he 
speaks  of  this  as  the  product  of  the  interaction  of  the  salts 
which  he  dissolved  and  the  other  reagents  which  he  used, 
whatever  they  may  have  been.  He  has  therefore  to  resolve 
the  mixed  constituents  of  the  globe  into  their  elements, 
and  to  ascertain  the  properties  of  every  combination  of 
elements  which  can  exist,  whether  these  combinations  are 
separable  as  forms  of  matter  which  can  be  isolated  and 
set  aside  in  the  drawers  and  bottles  of  the  laboratory,  or 
whether  they  can  exist  as  separate  bodies  only  under  con- 
ditions which  render  their  isolation  impossible. 

But  in  chemistry,  as  in  all  other  branches  of  Natural 
Science,  the  observation  of  phenomena  provokes  reflec- 
tions as  to  their  cause.  Why  do  the  elements  combine? 
Why,  when  a  compound  has  been  formed,  is  it  ready 
under  certain  circumstances  to  exchange  one  of  its  elements 
for  another,  or  to  react  with  some  other  compound  in  such 
a  way  as  to  produce  either  a  more  complicated  compound, 
or  two  or  more  substances  which  do  not  resemble  either 
of  those  from  which  they  are  derived?  Chemical  philos- 
ophy is  occupied  with  many  problems ;  but  the  one  which 
is  most  distinctly  chemical  is  the  determination  of  the 
positions  which  the  elements  in  a  compound  occupy  rela- 
tively to  one  another,  the  architecture  of  derived  substances, 
as  it  may  be  termed.  It  is  necessary  to  think  of  matter 
as  composed  of  atoms,  whatever  may  be  the  nature  of 
these  units  of  structure.  If  our  powers  of  vision  were  suf- 
ficiently increased,  we  should  see  matter,  not  as  we  see 
treacle,  but  as  we  see  marbles  when  enclosed  in  a  vase  of 
clear,  transparent  glass  ;  with  this  difference,  that  the  mar- 


76  AN    INTRODUCTION    TO    SCIENCE 

bles  would  not  be  in  contact  with  one  another,  but  sepa- 
rated by  vacant  space,  and  not  at  rest  but  in  a  state  of 
perpetual  motion.  The  intervals  between  the  marbles  (not 
the  size  of  the  marbles)  would  vary  according  as  the  matter 
was  in  a  solid,  liquid  or  gaseous  state.  They  would  also 
be  proportional  to  the  amount  of  heat  in  the  body.  The 
hotter  the  body  the  more  rapidly  its  particles  move ;  the 
more  rapidly  they  move  the  greater  are  the  intervals  which 
separate  them,  or  vice  versa.  But  if  our  power  of  vision 
were  still  further  increased  we  should  see  that  each  marble 
is  a  group  of  smaller  bodies,  still  not  in  contact,  but  sepa- 
rated one  from  the  other  by  very  much  smaller  spaces  than 
those  which  separate  the  marbles.  In  chemical  language, 
matter  is  composed  of  molecules,  and  molecules  of  atoms. 
The  chemist  attributes  the  properties  of  matter  to  the 
arrangement  of  the  atoms  in  its  molecules.  He  believes 
that  when  he  changes  the  nature  of  a  substance  —  when 
he  alters  its  properties,  that  is  to  say  —  he  changes  either 
the  number  or  the  kind  of  atoms,  or  their  mutual  arrange- 
ment in  the  molecule ;  for  he  has  the  best  of  reasons  for 
thinking  that  a  molecule  does  not  consist  of  a  certain 
number  of  elementary  atoms  arranged  at  haphazard,  as 
stones  of  several  kinds  might  be  thrown  into  a  sack,  but 
that  the  atoms  are  put  together  according  to  a  plan  so 
definite  that  no  two  atoms  could  change  places  in  a  mole- 
rule  without  an  alteration  in  the  properties  of  the  sub- 
stance. 

There  are  certain  substances,  in  number  about  seventy, 
which  cannot  be  changed  one  into  another.  These  are  the 
chemical  " elements."  Until  the  seventeenth  century  all 
forms  of  matter  were  supposed  to  be  transmutable.  Aris- 
totle taught  that  there  is  only  one  fundamental  matter  which 
is  united  in  Nature  with  varying  quantities  of  the  four 
"elementary  principles,"  earth,  fire,  air,  water;  and  that 
the  properties  which  different  forms  of  matter  present 
depend  upon  the  relative  amounts  of  the  several  elementary 


ULTIMATE    CONSTITUTION   OF    MATTER        77 

principles  impressed  upon  them.  We  may  look  upon  this 
ancient  doctrine  ( which  had  an  oriental  origin  long  before 
Aristotle's  time)  as  a  transcendental  explanation  of  the 
Nature  of  Matter  starting  from  physical  data.  The  alche- 
mists, substituting  ideas  which  may  be  called  chemical,  little 
as  they  resemble  the  clear  conceptions  of  modern  chemistry, 
assigned  the  differences  in  property  of  the  metals  to  their 
possessing  the  three  "Chymical  principles,"  salt,  sulphur 
and  mercury,  in  varying  degrees.  Such  notions  seem  to  us 
to  be  wide  of  the- mark  ;  but  if  we  try  to  imagine  ourselves 
as  living  in  the  days  before  the  principle  of  the  Conservation 
of  Matter  was  determined,  we  shall  see  that  the  permanence 
of  Aristotle's  elements  could  be  assumed  with  a  greater 
show  of  reason  than  the  permanence  of  matter.  The  com- 
position of  the  air  was  known  no  better  than  the  composi- 
tion of  flame.  A  piece  of  wood  when  ignited  was  converted 
into  flame  save  for  a  little  residue  of  ash.  Clearly  it  con- 
sisted of  ash,  or  earth,  and  flame.  Boyle  founded  modern 
chemistry  when,  in  language  free  from  ambiguity  and 
mysticism,  he  enunciated  the  theory  that  there  are  certain 
indestructible  substances  which  cannot  be  resolved  into 
simpler  constitutents  or  transmuted  one  into  the  other. 
Such  truly  unchangeable  substances  are  properly  entitled  to 
the  name  of  "Element." 

Since  they  cannot  be  broken  up  into  simpler  bodies,  the 
chemist  accepts,  provisionally,  the  doctrine  that  all  the 
atoms  which  compose  any  given  element  are  uniform  in 
shape  and  size,  and  are  in  every  other  respect  of  the  same 
kind.  He  is  aware  that  certain  elementary  bodies,  such  as 
carbon,  boron,  phosphorus,  exist  in  more  than  one  modifi- 
cation or  state,  as  different  in  properties  as  soot  and 
diamond  (in  the  case  of  carbon),  but  for  purposes  of  cal- 
culation, he  speaks  of  the  atoms  of  each  particular  element 
as  if  they  were  truly  unalterable,  or  at  any  rate  truly 
indivisible.  The  language  and  formulae  of  chemistry  imply 
that  every  element  has  its  own  specific  atom,  which  differs  in 


;8  AN  INTRODUCTION   TO    SCIENCE 

size,  and  therefore  in  all  its  properties,  from  the  atoms  of 
every  other  element.  If  it  were  possible  for  us  to  see  the 
atoms,  we  could  with  a  certain  scale  of  relative  sizes  (atomic 
weights)  say  which  atoms  were  those  of  phosphorus,  which 
of  silver,  and  so  on. 

Before,  therefore,  he  studies  the  architecture  of  matter, 
the  chemist  examines  the  constructive  materials  which 
Nature  uses.  He  finds  that  she  builds  with  some  seventy 
different  elements.  As  we  have  already  said,  he  recognises 
each  of  these  various,  elements  by  the  size  of  the  atoms  of 
which  it  is  composed. 

It  has  long  been  suspected  that  the  chemical  unit  or  atom 
is  not,  as  its  name  implies,  "an  ideally  indivisible  portion  of 
matter."  On  the  contrary,  it  would  seem  that  the  true  atom 
cannot  under  any  conditions  be  made  to  act  as  a  unit. 
Nature  has  arranged  the  true  atoms  into  groups,  which 
always  act  as  groups,  and  each  of  which  is  therefore,  for  all 
practical  purposes,  an  atom.  We  cannot  break  up  the 
groups,  and  we  can  conceive  them  as  divisible  only  in  a 
universe  quite  different  to  the  universe  that  we  know. 

According  to  this  modern  conception  of  the  nature  of 
matter,  there  is  but  one  fundamental  substance,  protyle. 
This  arch-element  does  not  exist  except  in  various  states  of 
condensation  or  groupings  of  atoms  held  together  by  indis- 
soluble bonds.  The  "atoms  "  of  all  the  elements,  even  the 
lightest  of  them,  hydrogen,  are  aggregations  of  protyle- 
atoms. 

We  owe  this  conception  of  an  arch-element  in  various 
fixed  degrees  of  condensation  to  Mendeleef's  discovery 
that  all  the  elements  with  which  we  are  acquainted  can  be 
arranged  in  series  according  to  the  numerical  value  of  their 
atomic  weights.  The  chemist  cannot  estimate  the  weight 
of  an  atom,  but  he  can  determine  the. amount  of  any  given 
element,  which  enters  into  combination  with  other  elements, 
relatively  to  the  amounts  of  the  elements  with  which  it 
combines.  Dalton  (1802)  pointed  out  that  if  all  possible 


ULTIMATE    CONSTITUTION   OF    MATTER        79 

compounds  of  oxygen,  hydrogen,  chlorine,  lead,  etc.,  are 
made  by  the  chemist,  and  then  the  compounds  are  isolated 
in  a  pure  state  and  analysed,  the  superfluous  substances 
which  have  not  entered  into  combination  being  removed,  it 
will  be  found  that  whatever  the  amount  (relatively  to  any 
arbitrary  standard)  of  the  element  utilised,  it  will  always  be 
either  this  amount,  say  x  or  some  simple  multiple  of  this 
amount,  say  2^r,  3-r,  43?.  For  example,  nitrogen,  which  is  a 
monovalent  atom,  combines  with  the  divalent  atom  of 
oxygen  to  form  the  compound  N2O5.  With  more  nitrogen 
and  less  oxygen,  the  compounds  N2O4,  N2O3,  NO,  N2O  are 
formed ;  but  there  are  no  compounds  of  nitrogen  and 
oxygen  which  contain  a  larger  proportion  of  nitrogen  than 
does  the  compound  N2O,  or  a  larger  proportion  of  oxygen 
than  N2O5.  So  simple  are  the  multiples  that  if  the  chemist, 
wishing  to  play  at  making  compounds,  cuts  out  blocks  of 
wood  and  represents  each  of  the  elements  by  a  block  of  a 
particular  colour,  he  will  never  need  more  than  six  blocks 
of  any  given  colour  to  build  up  all  the  compounds  with 
which  Dalton  was  acquainted.  Since  Dalton's  time  a  small 
number  of  more  complicated  combinations,  such  as  the 
complex  silicates  and  phosphomolybdates,  have  been  dis- 
covered, but  his  law  still  holds  good  for  the  vast  majority 
of  inorganic  substances.  This  is  the  basis  of  the  atomic 
theory.  It  makes  it  possible  to  denote  the  elements  by 
symbols :  O  for  oxygi  n,  H  for  hydrogen,  Fe  for  iron 
(ferrum)  etc.,  and  to  express  their  combinations  as  OH2, 
FeO,  Fe2O3,  Fe3O4,  Fe2O3H2O,  etc. 

If  any  arbitrary  unit  be  chosen,  if,  for  example,  it  be 
assumed  that  the  weight  of  the  atom  of  the  lightest  element, 
hydrogen,  is  i,  then  it  follows  that  in  any  compound  in 
which  there  are  exactly  the  same  number  of  atoms  of 
hydrogen  as  of  some  other  element,  the  actual  weight  of 
the  other  element  found  in  the  compound  is  to  the  actual 
weight  of  the  hydrogen  as  the  weight  of  the  atom  of  the 
other  element  to  the  weight  of  the  atom  of  hydrogen.  For 


So  AN   INTRODUCTION    TO    SCIENCE 

example,  if  we  have  reason  to  believe  that  hydrochloric  acid 
gas  is  formed  by  the  union  of  hydrogen  atoms  and  chlorine 
atoms  in  equal  numbers,  its  formula  may  be  expressed  as 
HC1 ;  and  if,  when  it  is  analysed,  this  gas  is  found  to  contain 
by  weight  35^  times  as  much  chlorine  as  hydrogen,  the 
atom  of  chlorine  weighs  35^  in  the  hydrogen  scale. 

We  may  digress  for  a  moment  to  explain  how  it  comes  to 
be  possible  to  ascertain  whether  the  same  number  of  atoms 
of  two  elements  are  in  combination,  or  unequal  numbers. 
Cavendish  found  that  when  he  filled  a  globe  with  a  mixture 
of  pure  hydrogen  and  pure  oxygen  in  the  proportion  of  2 
cubic  inches  of  hydrogen  for  every  i  cubic  inch  of  oxygen, 
and  exploded  the  mixture,  nothing  remained  but  water. 
Except  for  the  water-vapour  the  globe  was  empty.  It  could 
be  refilled  with  the  same  mixture  over  and  over  again,  and 
yet  after  several  explosions  nothing  remained  in  it  but 
water.  Gay-Lussac  and  Humboldt  (1805)  repeated  this  ex- 
periment, not  only  with  hydrogen  and  oxygen,  but  with  hy- 
drogen and  chlorine,  and  various  other  gases  which  combine 
to  form  gaseous  products,  and  they  found  that  the  volumes 
of  any  two  gases  which  must  be  used  if  a  compound  is  to  be 
formed  and  no  remainder  left  over,  bear  such  simple 
numerical  relations  one  to  another,  as  i  :  i,  2  :  i,  3  :  4, 
etc.  This  discovery,  considered  in  its  bearing  upon  Dai- 
ton's  observation  that  the  proportions  by  weight  in  which 
any  given  element  enters  into  the  formation  of  several  dis- 
tinct compounds,  bear  very  simple  numerical  relations  one 
to  another,  led  to  the  formulation  by  Berzelius  of  Uie 
theorem  that  equal  volumes  of  gases  contain  equal  numbers 
of  atoms.  Berzelius'  generalisation  was  fallacious,  because 
he  did  not  know  that  even  in  the  gaseous  elements  the 
atoms  are  not  isolated  but  combined  into  molecules.  When 
Avogadro  substituted  the  word  molecule  for  atom,  and  said 
that  "equal  volumes  of  all  gases  contain  equal  numbers  of 
molecules,"  the  theorem  assumed  an  expression  which  is 
subject  to  no  dispute.  No  matter  what  gas  is  put  into  a 


ULTIMATE    CONSTITUTION    OF   MATTER        Si 

given  space,  or  what  its  weight,  the  gas  is  always  composed 
of  a  certain  fixed  (though  not  ascertained)  number  of  mole- 
cules, provided  the  pressure  and  temperature  are  constant. 
Therefore  one  gas  is  heavy  and  another  light,  because  in  the 
one  the  molecules  are  large,  in  the  other  small.  A  gas  is  a 
gas  (and  not  a  solid  or  a  liquid)  because  its  molecules  repel 
one  another.  When  pressure  is  put  upon  a  gas  its  mole- 
cules are  squeezed  nearer  together,  and  the  amount  by 
which  they  are  approximated  varies  directly  as  the  amount 
of  pressure.  Again,  when  a  gas  is  heated  the  mutual  re- 
pulsion of  the  molecules  is  increased,  and  the  force  of  re- 
pulsion is  exactly  proportional  to  the  temperature.  When 
air  is  heated  from  o°  C.  to  i°  C.  it  expands  by  ^  of  its 
volume,  and  if  it  be  heated  from  95°  C.  to  96°  C.,  its  volume 
is  increased  by  exactly  the  same  amount.  But  owing  to  the 
fact  that  the  atoms  of  some  gases  are  heavy  while  those  of 
other  gases  are  light,  it  takes  more  heat  to  raise  the  tem- 
perature of  the  former  than  of  the  latter.  If  it  were  desired 
to  raise  the  temperature  of  two  gases  i°,  a  spirit  lamp 
would  need  to  be  kept  just  as  much  longer  under  a  vessel 
filled  with  the  gas  made  of  heavy  atoms  than  under  the  gas 
made  of  light  atoms,  as  the  atoms  were  heavier  in  the  one 
case  than  in  the  other.  In  other  words,  the  atomic  weight 
of  a  gas  divided  by  its  specific  heat  gives  a  constant  number 
as  dividend.  All  lines  of  evidence  converge  to  support  the 
modern  view  that  matter,  in  a  gaseous  state,  consists  of 
separate  molecules,  or  groups  of  atoms,  which  are  at  the 
same  distance  apart  in  all  gases  under  the  same  conditions 
of  temperature  and  pressure  ;  and  therefore  that  the  weight 
of  a  gas  depends,  not  upon  the  number  of  the  molecules 
which  it  contains,  but  upon  the  weight  of  each  molecule. 
From  this  it  follows  that  there  can  be  no  uncertainty  as  to 
the  molecular  weight  of  any  element  if  it  can  be  examined 
in  the  gaseous  state.  It  is  directly  proportional,  both  to  its 
specific  gravity  and  to  its  specific  heat.  The  molecule  of 
every  element  when  in  a  gaseous  state  is  a  group  of  two 


82  AN  INTRODUCTION    TO    SCIENCE 

atoms ;  with  the  exception  of  the  gas,  argon,  which  Lord 
Raleigh  and  Professor  Ramsay  have  recently  discovered  in 
the  atmosphere,  which  is  monatomic,  and  sodium  and  potas- 
sium (and  probably  other  elementary  gases),  which  become 
monatomic  at  high  temperature.  In  the  cases  of  elements 
which  cannot  be  converted  into  gas,  the  molecular  weight 
must  of  course  be  determined  by  indirect  methods. 

A  study  of  the  numerical  relations  between  the  atomic 
weights  of  the  elements  led  Mendele"ef  to  the  greatest 
generalisation  of  Modern  Chemistry  —  the  formulation  of 
the  "Periodic  Law."  This  generalisation  more  than  any 
other  has  given  rise  to  speculation  as  to  the  ultimate  con- 
stitution of  matter.  It  seems  to  be  a  logical  inference  from 
the  periodic  relations  between  them,  that  the  atoms  of  all 
chemical  elements  are  really  clusters  of  atoms  of  the  funda- 
mental substance,  protyle.  If  this  be  true,  the  indestructi- 
bility and  immutability  of  an  element  means  the  indivisibility 
by  chemical  means  of  the  protyle  cluster.  Neglecting  all 
qualifications,  the  Periodic  Law  may  be  explained  as 
follows : 

Mendeleef  s  Law  (1869).— The  atomic  weights  of  the 
elements  (on  the  hydrogen  scale)  range  from  hydrogen,  i,  to 
uranium,  240.  They  might  therefore  be  arranged  in  a  linear 
series.  But  a  consideration  of  their  properties  shows  that 
the  elements  fall  into  groups.  If  any  property  common  to 
all  elements  be  considered,  and  a  band  varying  in  width 
according  to  the  degree  in  which  they  severally  exhibit  this 
property  be  drawn  down  the  full  length  of  the  list,  it  will  be 
found  that  prominences  and  subsidences  occur  at  intervals 
on  the  band.  No  matter  whether  we  are  comparing  the 
elements  with  regard  to  the  melting  points  and  boiling 
points  of  certain  of  their  compounds,  the  heat  evolved  dur- 
ing their  union  with  chlorine,  their  spectra,  the  colours  of 
certain  of  their  salts,  their  magnetic  properties,  or  their  oc- 
currence in  Nature,  we  find  that  the  line  representing  the 
quality  of  the  character  or  the  amount  of  its  development 


ULTIMATE    CONSTITUTION    OF    MATTER        83 

undulates  down  the  list.  And  the  importance  of  this  com- 
parison becomes  apparent  when  it  is  noticed  that  the  periods 
of  maximum  and  minimum  prominence  of  all  these  dif- 
ferent characters  approximately  coincide. 

To  take  an  illustration  from  acoustics  :  Each  tone  of  the 
diatonic  scale  has  its  own  rate  of  vibration,  but  each  tone  is 
not  a  separate  thing  unrelated  to  all  other  tones.  Some  can 
be  sounded  in  harmony,  others  cannot.  So  also  the  gamut 
of  the  elements  may  be  divided  into  groups,  which  strangely 
resemble  octaves.  Perhaps  this  analogy  which  has  attracted 
the  attention  of  many  chemical  philosophers  is  more  than 
superficial;  for  the  properties  of  the  elements  also  depend 
upon  the  vibration  periods  of  their  molecules. 

The  observation  that  the  properties  of  the  elements,  as 
well  as  those  of  their  compounds,  are  periodic  functions  of 
the  atomic  weights  of  the  elements — that  the  properties  of 
the  elements  are  determined  by  their  atomic  weights,  that  is 
to  say — led  Mendele*ef  to  classify  them  as  follows:  He 
ruled  a  sheet  of  paper  into  eight  vertical  and  twelve  hori- 
zontal columns.  In  the  ninety-six  places  thus  provided  he 
disposed  the  elements  according  to  their  atomic  weights,  the 
lightest  being  in  the  top  left-hand  square,  the  heaviest  in  the 
bottom  right-hand  square.  The  eight  vertical  columns  he 
termed  "groups,"  the  twelve  horizontal  columns  "series." 
The  reader  must  not,  however,  think  that  this  arrangement 
could  be  carried  out  on  any  simple  arithmetical  basis. 
There  were,  and  still  are,  many  difficulties  and  reasons  for 
uncertainty.  For  example  — 

(1)  The  eighth  element  in  each  alternate  series  exhibits 
properties  which  would  equally  justify  its  inclusion  as  the 
first  of  the  next.     It  is  therefore  duplicated,  and  appears  in 
both. 

(2)  Certain  metals  so  closely  resemble  the  duplicated 
members  that  they  have  to  be  included  with  them  in  the 
eighth  column.     Thus  iron,  nickel  and  cobalt  appear  in 
the  same  square  as  copper. 


84  AN   INTRODUCTION   TO    SCIENCE 

(3)  Hydrogen  and  the  gas,  helium  (At.  W.  4),  recently 
discovered  by  Professor  Ramsay,  stand  alone  in  the  first 
series,  no  other  member  of  this  series  being  known. 

(4)  There  were  several  gaps  in  the  table,  of  which  some 
have  since  been  filled  up. 

(5)  The  differences  between  the  atomic  weights  of  the 
several  members  of  each  series  or  of  each  group  are  only 
approximately  constant. 

Despite  its  want  of  arithmetical  rigidity,  there  can  be 
no  doubt  that  Mendele*efs  classification  is  based  upon 
natural  laws.  The  elements  which  he  arranged  in  groups 
resemble  each  other  in  properties ;  their  differences  are 
differences  in  degree.  The  elements  in  the  series  differ 
from  one  another  in  properties,  and  the  amount  of  their 
differences  increases  progressively  from  the  first  to  the 
seventh  or  eighth  member.  Their  properties  therefore  vary 
in  kind. 

Take,  as  an  example  of  properties,  the  tendency  to  form 
oxides.  Most  of  the  elements  form  more  than  one  oxide, 
but  for  each  of  them  there  is  one  oxide  which  chemists 
regard  as  characteristic.  If  R  stands  for  any  element,  the 
characteristic  oxide  of  group  I.  is  R2O ;  of  II.,  R2O2 ;  of 
VII.,  R2O7. 

If  we  compare  the  hydrogen-holding  power  of  the 
elements  with  their  oxygen-holding  power,  we  find  that 
their  capacities  in  this  respect  are  reversed.  The  hydrides 
of  group  VII.  have  the  formula  RH ;  of  VI.,  RHo ;  cf  V., 
RH3;  and  of  IV.,  RH4.  The  justification  of  the  octave 
arrangement  is  shown  very  clearly  by  these  two  sets  of 
compounds.  No  single  atom  of  any  element  can,  so  far  as 
is  known,  combine  with  more  than  four  atoms  of  oxygen, 
or. with  more  than  four  atoms  of  hydrogen  ;  but  if  its  maximum 
hydrogen-holding  power  and  its  maximum  oxygen-holding 
power  are  considered  together,  it  is  found  that  the  number 
of  atoms  of  hydrogen  which  it  can  hold,  plus  twice  the 
number  of  atoms  of  oxygen  (because  O  is  divalent),  always 


ULTIMATE    CONSTITUTION    OF    MATTER        85 

equals  8.  To  take  illustrations  from  each  of  the  groups 
IV.,  V.,  VI.,  VII.,  we  find  that  carbon  forms  CH4  and  CO2, 
nitrogen  NHa  and  N2O5,  sulphur  SOs  and  SH2,  and  iodine 
I2O7  and  IH. 

As  yet  the  expression  of  the  Periodic  Law  is  tentative 
and  provisional.  The  fact  that  it  explains  many  hitherto 
inexplicable  phenomena  indicates  that,  when  it  is  completely 
and  justly  formulated,  it  will  account  for  many  more.  It 
exemplifies  the  grand  function  of  Science,  to  marshal  the 
apparently  unrelated  and  uncoordinated  facts  of  the  uni- 
verse. Boyle's  rabble  of  elements  is  already  a  disciplined 
army.  The  discovery  of  the  ' '  periodicity ' '  of  their  properties 
has  given  the  chemist  an  entirely  new  grasp  of  the  elements. 
As  a  mere  memoria  technica,  Mendeleef  s  table  is  of  immense 
value  to  the  student.  Any  element  of  which  he  thinks  is 
no  longer  an  isolated  unit,  with  properties  peculiar  to  itself. 
Its  place  in  the  table  shows  him  what  its  characters  must  be, 
relatively,  both  to  the  horizontal  series  and  to  the  vertical 
group  to  which  it  belongs.  But  the  Periodic  Law,  although 
we  do  not' yet  know  its  full  meaning,  is  far  more  than  an 
aid  to  the  memory.  It  is  prophetic  as  well  as  retrospective 
or  explanatory.  It  has  called  attention  to  many  of  the 
shortcomings  of  chemical  science,  and  foretold  how  they 
may  be  corrected.  The  incorrect  atomic  weights  of  elements 
which  would  not  fit  into  the  scheme  have  been  set  right. 
The  existence  of  vacant  spaces  in  the  table  has  led  to  the 
search  for  new  elements ;  it  has  indicated  their  alliances, 
pointed  to  the  minerals  in  which  they  might  be  looked  for, 
and  thus  led  to  their  discovery.  Compounds  which  were 
supposed  not  to  exist  have  been  found  after  the  position  of 
an  element  in  a  group  which  usually  formed  such  compounds 
had  been  admitted. 

If  Mendeleef's  theory  is  correct,  it  follows  that  the 
number  of  elements  is  strictly  limited.  Some  of  them 
have  not  yet  been  discovered,  but  Mendeleef's  prophecy 
that  the  vacant  spaces  will  be  gradually  filled  has  already 


86  AN    INTRODUCTION    TO    SCIENCE 

been  verified  in  certain  cases.  New  elements  have  been 
found  which  have  the  atomic  weight  and  the  properties 
foretold  of  missing  members  of  the  series.  But  what  is  to 
be  done  in  the  event  of  several  claimants  demanding  to  be 
admitted  to  the  same  place?  This  is  a  problem  which 
chemists  have  to  face.  A  very  rare  metal,  yttrium,  has 
been  resolved  by  successive  ' '  fractionations' '  into  seven 
metals  (of  which  one,  scandium,  was  wanted  to  fill  a  vacant 
place  in  Mendele*efs  table)  which  differ  but  very  slightly 
one  from  another.  By  fractionation,  to  take  a  simple 
example,  is  meant  such  a  process  as  forming  a  nitrate  of 
the  metal,  and  then  heating  this  salt  to  a  certain  tempera- 
ture which  is  not  sufficiently  high  to  allow  of  the  conversion 
of  the  whole  of  the  nitrate  into  oxide.  Some  is  decomposed, 
while  the  rest  remains  as  nitrate,  which,  being  a  soluble 
salt,  can  be  dissolved  in  water.  This  dissolved  nitrate  is 
crystallized  and  heated  somewhat  more  strongly,  and  the 
process  repeated  over  and  over  again.  And  of  the  seven 
new  metals,  the  real  yttrium,  as  judged  by  the  spectroscope, 
shows  indications  of  being  a  mixture  of  five  metals  which 
cannot  be  distinguished  by  chemical  methods.  It  might  be 
inferred  that  this  apparent  multiplicity  of  metals  could  be 
explained  as  due  to  the  failure  on  the  part  of  the  chemist  to 
remove  impurities  ;  but  Sir  William  Crookes  is  not  content 
with  this  explanation.  He  believes  that  the  chemical  atom 
of  the  element  yttrium  is  not  fixed  ;  that  the  number  of  pro- 
tyle  atoms  which  form  its  cluster  varies,  and  that  the  five 
"meta-elements"  are,  as  it  were,  either  trying  to  fix  into 
an  element,  or  that,  like  a  very  rare  species  of  animal  (the 
mud-fish,  for  example),  which  is  dying  out  because  it  is  not 
fitted  for  its  environment,  it  is  exhibiting  great  variability 
in  its  expiring  efforts  to  hold  its  own  against  its  better 
equipped  competitors.  These  far-reaching  speculations  of 
Sir  William  Crookes  bring  the  analogies  of  living  phe- 
nomena into  the  inanimate  world.  He  speaks  of  the 
origin,  predominance  and  decay  of  the  elements  in  the 


ULTIMATE   CONSTITUTION    OF   MATTER        87 

same  terms  in  which  a  naturalist  describes  the  struggle  for 
existence. 

Each  year  our  conceptions  with  regard  to  the  structural 
constitution  of  matter,  its  architecture,  become  more  defi- 
nite. With  the  mind's  eye  we  not  only  see  it  composed  of 
separate  molecules,  but  we  can  tell  approximately  how  the 
atoms  are  placed  in  the  molecule.  We  can  figure  to  our- 
selves the  shape  of  the  atom-groups. 

For  a  long  time  chemists  have  denoted  compounds  by 
graphic  formulae.  They  have  replaced  the  name  of  a  sub- 
stance by  an  ideo-graph,  which  shows  the  number  of  atoms 
of  each  element  in  its  molecule.  Thus,  ammonia  is  NH3 ; 
and  aniline  is  written  N  (C0H5)  H2  to  show  that  one  of 
the  three  H's  in  ammonia  is  replaced  by  the  radicle,  ben- 
zene. Various  diagrams  are  made  to  indicate  that  some 
elements  can  unite  with  one  combining  unit  of  hydrogen, 
while  others  will  take  two,  three,  or  four.  The  atoms  are 
represented  as  having  one  or  more  affinities,  to  which  other 
atoms  or  radicles  can  be  attached.  The  atom  of  carbon  is 
tetravalent,  and  since  each  of  its  four  affinities  may  be  satis- 
fied with  a  different  element  or  group  of  elements,  its 
compounds  are  exceedingly  complex.  The  molecules  of 
all  so-called  "organic"  bodies  are  clusters  of  carbon-atoms 
united  with  hydrogen,  oxygen  or  nitrogen,  or  with  all  three 
of  these  elements,  and  in  rare  cases  with  a  metal  in  addi- 
tion. Now,  it  is  clear  that  a  molecule  must  occupy  three 
dimensions  in  space ;  and  if  the  chemist  wishes  to  picture 
its  form  he  must  use,  not  a  flat  diagram,  but  a  solid  model. 
He  must  take  a  stereoscopic  view  of  the  molecule.  Hence 
the  science  of  the  architecture  of  matter  of  the  position  of 
atoms  in  space,  is  termed  stereochemistry. 

That  stereochemistry  is  more  than  an  arbitrary  system  of 
symbols,  that  it  is  really  possible  to  ascertain  the  relative 
positions  of  the  atoms  which  compose  a  molecule,  and 
therefore  to  form  a  conception  of  its  shape,  was  first  indi- 
cated by  an  observation  made  by  Pasteur  fifty  years  ago.  It 


88  AN  INTRODUCTION   TO    SCIENCE 

was  known  at  that  time  that  certain  compounds  when  in 
solution  rotate  the  plane  of  polarized  light.  The  undula- 
tions which  constitute  a  ray  of  light  are  in  all  planes ;  but  if 
the  ray  is  passed  through  a  plate  of  the  semi-transparent 
mineral  tourmaline,  cut  parallel  to  its  axis,  only  those  vibra- 
tions which  are  in  planes  coinciding  more  or  less  with  the 
axis  of  the  crystal  pass  through  it — to  vibrations  in  other 
planes  tourmaline  is  opaque  —  and,  in  passing  through, 
they  are  turned  until  they  are  all  quite  parallel.  The  mineral 
acts  as  an  optical  sieve.  If  now  these  polarized  rays  are 
passed  through  certain  substances  in  solution,  or  in  the 
CKystalline  form,  they  are  twisted  to  the  right  or  to  the  left. 
Pasteur  discovered  that  there  are  two  kinds  of  tartaric  acid, 
distinguished  when  in  solution  by  the  fact  that  the  one 
rotates  a  ray  of  polarized  light  to  the  right  and  the  other 
rotates  it  to  the  left ;  and  he  found  that  these  two  forms  of 
the  acid  (which  appear  to  be  absolutely  identical  in  chemi- 
cal properties  as  well  as  in  specific  gravity  and  other 
physical  properties)  differ  when  crystallized  to  this  extent 
—  the  laevo-rotary  crystals  look  like  the  dextro-rotary  when 
they  are  seen  in  a  looking-glass.  They  are  reversed  or 
enantiomorphic,  in  the  language  of  crystallography.  This, 
of  course,  implies  that  they  are  asymmetrical. 

There  are  two  forms  of  ethylidene  lactic  acid,  to  take 
another  example,  the  one  dextro-rotary  and  the  other  Isevo- 
rotary.  In  this  substance  the  tetravalent  atom,  carbon, 
has  its  four  affinities  satisfied  with  H,  OH,  CH3,  and  COOH, 
respectively.  To  gain  an  idea  of  the  way  in  which  these 
radicles  are  attached  to  the  carbon  atom  —  of  what  is  meant 
by  stereochemistry  —  the  reader  may  cut  out  a  tetrahedron 
in  wood.  If  he  then  sticks  pins  with  little  heads  (H  =  i) 
and  with  big  heads  (C  =  12  and  O  =  16)  into  the  corners  of 
the  four-sided  block  to  represent  the  four  radicles  with 
which  the  carbon  is  united,  the  lob-sided  model  which  he 
makes  may  stand  for  one  of  the  two  varieties  of  lactic  acid, 
say  the  dextro-rotary.  If  the  dextro-rotary  model  be  held 


ULTIMATE    CONSTITUTION    OF    MATTER        89 

before  a  mirror,  a  model  of  the  laevo-rotary  acid  is  seen.  Of 
course  we  know  nothing  as  to  the  real  form  of  any  molecule, 
but  we  may  claim  to  have  something  better  than  a  vague 
idea  of  what  the  molecules  of  different  substances  are  rela- 
tively like.  The  science  of  stereochemistry  is  the  product 
of  a  vast  amount  of  chemical,  mathematical  and  physical 
research.  Already  very  complicated  molecular  figures  have 
been  worked  out,  and  the  subject  promises  most  important 
generalisations  in  the  future. 


CHAPTER    V 
Origin  of  Species 

Two  hundred  thousand  species  of  insects  are  known, 
and  it  is  estimated  that  450,000  animals  in  all  have  been 
described  and  named.  The  Kew  catalogue  of  flowering 
plants  records  120,000  species,  and  probably  the  plants 
which  do  not  flower  are  equally  numerous.  The  total 
number  of  animals  and  plants  already  recognised  as  distinct 
and  separate  forms  is  about  three-quarters  of  a  million,  and 
none  can  say  how  many  yet  remain  to  be  described.  To 
classify  all  these  various  forms  of  living  things  according  to 
some  intelligible  scheme,  is  the  business  of  the  student  of 
animated  nature  ;  at  first,  in  ignorance  of  any  cause  for  their 
diversity  of  form,  botanists  and  zoologists  thought  only  of 
so  arranging  them  that  they  might  know  where  to  look  for 
them  in  their  museums,  and  how  to  find  the  name  of  any 
particular  form  which  was  not  familiar,  or  to  make  sure  that 
it  had  not  hitherto  been  described  and  named.  Thus  we 
find  Linnaeus  arranging  plants  into  ' '  orders, ' '  according 
to  the  number  of  their  stamens — as  we  might  classify  our 
friends  according  to  the  number  of  letters  in  their  names. 
Truly  such  a  classification  would  be  useful.  We  should  get 
all  the  Smiths  into  one  group  and  all  the  Robinsons  into 
another,  and  when  we  saw  a  man  with  the  Macgillicuddy 
features  coming  down  the  road,  we  should  at  once  think  of 
him  as  belonging  to  one  of  the  many-lettered  groups,  and 
should  know  approximately  in  which  album  to  look  for 
photographs  of  his  near  relations.  But  we  should  find  the 

(90) 


CHARLES  DARWIN. 
1809-1882. 


ORIGIN    OF   SPECIES  91 

five-lettered  and  six-lettered  groups  extremely  cumbrous,  as 
Linnaeus  found  his  orders  Pentandria  and  Hexandria. 

De  Candolle  made  an  immense  advance  when,  in  1809,  he 
pointed  out  that  plants  have  certain  natural  affinities,  and 
that  therefore  they  should  be  classed  according  to  the  sum 
of  these  affinities.  It  is  only  in  this  way  that  a  "natural 
classification ' '  can  be  drawn  up ;  but  De  Candolle  be- 
queathed to  his  successors  an  almost  endless  task.  How  is 
the  sum  of  natural  affinities  to  be  measured  ?  How  is  the 
product  of  so  many  variants  to  be  estimated  ?  Root,  stem, 
branching,  thorns,  leaves,  stipules,  bracts,  inflorescence, 
calyx,  corolla,  stamens,  carpels,  placentation,  fruits,  verna- 
tion, aestivation  ;  it  is  impossible  to  give  a  numerical  value 
to  each  of  these  variable  organs  or  characters.  Who  is  to 
decide  whether  and  to  what  extent  marked  similarity  in  one 
character  shall  outweigh  dissimilarity  in  many  others. 
Imagine  two  examiners  differing  as  to  whether  A  or  B  shall 
have  a  prize  ?  (We  are  about  to  spoil  a  well-known  story. ) 
"I  have  given  B  more  marks  than  A,"  says  one,  "and  if 
we  add  your  marks  to  mine  B  still  comes  out  first,  and  yet 
you  persist  that  A  is  the  cleverer  boy.  On  what  do  you 
base  your  conviction?"  "On  my  general  impression." 

"Mr. ,  if  your  examiners  had  trusted  to  their  general 

impression,  you  would  never  have  been  in  a  position  to 
examine  for  this  prize."  A  general  impression  has  no  value 
in  an  examination  unless  it  be  the  sum  of  a  number  of 
particular  impressions,  each  accurately  expressed  in  marks. 
There  is  no  conceivable  plan  by  which  the  value  of  variable 
characters  can  be  marked  for  purposes  of  classification. 

With  the  publication  of  the  "Origin  of  Species"  (1859) 
the  problems  of  classification  acquired  an  entirely  new  and, 
for  the  first  time,  a  really  natural  aspect.  So  much  clearer 
and  more  comprehensive  was  Charles  Darwin's  theorem  of 
Natural  Selection  than  any  of  the  statements  of  Erasmus 
Darwin,  Lamarck,  St.  Hilaire  and  others  who  had  recog- 
nised that  the  fact  of  the  variability  of  species  indicates  a 


92  AN    INTRODUCTION    TO    SCIENCE 

"progressive  transmutation,"  that  for  all  practical  purposes 
it  is  the  starting-point  of  the  "new  biology."  And,  although 
Wallace  shares  equally  with  Darwin  the  credit  of  formu- 
lating the  law,  the  main  burden  of  its  proof  was  undertaken 
by  Darwin.  There  can  be  little  doubt  that  a  century 
hence,  when  minor  details  have  been  forgotten,  the  progress 
marked  by  the  enunciation  of  the  theory  of  Natural  Selec- 
tion will  be  regarded  as  the  greatest  event  in  the  history  of 
Science,  the  most  remarkable  step  forward  ever  taken. 

It  is  difficult  to  exaggerate  the  magnitude  of  the  change 
which  the  theory  of  Natural  Selection  brought  into  the 
naturalist's  attitude  of  mind  towards  the  subjects  of  his 
study.  It  gave  them  life.  The  wax-work  figures  which 
peopled  his  world  began  to  move.  Instead  of  each  indi- 
vidual form  standing  still,  finished,  immutable,  it  is  seen  to 
be  coming  out  of  a  past  and  progressing  towards  a  future. 
It  is  no  longer  a  perfected  thing  doing,  as  its  ancestors  have 
done,  the  work  for  which  it  was  designed ;  but  it  is  strug- 
gling towards  perfection  amidst  a  multitude  of  competitors. 
As  its  progress  becomes  faster,  its  species  spreads  over  the 
earth,  it  falls  behind  its  neighbours  in  capacity  for  adapta- 
tion, it  will  shrink  into  an  insignificant  remnant.  The 
stronger  plants  are  ousting  the  weaker  from  soil  and  sun- 
shine. Defenceless  plants  and  animals  are  growing  cleverer 
in  eluding  their  enemies.  Predatory  animals  are  becoming 
more  cunning  in  discovering  the  wiles  of  their  prey,  stronger 
in  jaw  and  claw  and  clasp  of  limb  to  pierce  their  armour. 
The  existence  of  every  living  thing  depends  upon  its  being 
able  to  obtain  its  food  and  to  resist  its  enemies.  The 
slightest  balance  in  its  favor  means  perpetuation,  the  least 
deficiency  leads  to  extinction.  Is  the  shell  of  a  mollusc 
strong  enough  to  resist  the  crushing  grip  of  a  lobster's  claw  ? 
Will  a  lobster's  carapace  withstand  the  horny  jaw  of  an 
octopus  when  its  eight  arms  envelop  it  in  their  paralyzing 
embrace  ?  Can  the  octopus  or  cuttle-fish  hide  its  soft  body 
from  the  dog-fish  in  search  of  food  by  suddenly  changing 


ORIGIN    OF    SPECIES  93 

colour  from  white  to  seaweed  brown,  or  by  projecting  into 
the  water  a  cloud  of  ink?  Our  forefathers,  watching  this 
inevitable  tyranny  of  strength  and  cunning,  felt  that  it  was 
cruel.  As  it  had  been  in  the  past  it  must  continue  to  be. 
The  weak  would  remain  weak  ;  the  strong  would  continue 
strong.  We  lose  the  idea  of  cruelty  in  the  interest  of  the 
competition.  It  is  a  race  for  perfection,  and  the  things 
which  fail  to  adapt  themselves  must  become  as  the  grap- 
tolites,  trilobites  and  ammonites,  which  have  long  since 
disappeared  from  the  earth. 

Further,  what  is  true  of  living  things,  looked  at  as  a 
whole,  is  true  of  every  organ  of  which  they  are  composed. 
Fifty  years  ago  it  was  the  custom  for  the  teacher  of  human 
anatomy,  after  saying  all  that  could  be  said  about  the  form 
and  structure  of  the  organs  which  were  the  subjects  of  the 
lesson  for  the  day,  to  dwell  upon  their  perfection  as  instru- 
ments designed  for  a  particular  work.  He  may  have  had 
his  doubts,  but  it  would  have  been  irreverent  to  express 
them.  Now,  when  he  touches  upon  the  mechanics  of  a 
bone,  say  the  scapula,  or  of  a  muscle  such  as  the  plantaris, 
he  is  free  to  say  of  the  former,  ' '  This  bone  is  entirely  wrong 
in  principle,  but  as  an  adaptation  of  the  scapula  of  a  quad- 
ruped, which  is  used  to  transfer  the  weight  of  the  trunk  to 
the  fore  limb,  it  serves  its  purpose,  namely,  to  swing  the 
fore  limb  on  the  trunk."  Or  of  the  latter,  "This  is  a 
muscle  which  was  of  use  in  lower  animals.  It  is  practically 
useless  in  Man,  and  will,  in  course  of  time,  be  discarded.  Its 
poor  development  and  irregular  origin  and  insertion  show 
that  it  is  on  the  point  of  disappearing."  There  is  not  an 
organ  in  the  body  which  is  perfect,  in  the  sense  of  having 
attained  to  finality,  and  there  are  many  which  are  evidently 
on  the  downward  grade.  Take,  as  an  example,  the  thymus 
gland,  an  organ  which  lies  behind  the  upper  part  of  the 
breastbone.  At  the  time  of  birth  this  organ  weighs  about 
half  an  ounce.  During  the  first  two  years  of  life  it  grows  as 
fast  as  other  organs  ;  after  five  it  rapidly  disappears.  It 


94  AN  INTRODUCTION   TO    SCIENCE 

consists  of  a  tabulated  mass  of  lymphoid  tissue  —  tissue, 
that  is  to  say,  in  which  young  white  blood-corpuscles,  or 
leucocytes,  are  being  formed.  Little  spherical  nests  of 
epithelial  cells  are  embedded  in  this  tissue,  as  well  as  a 
number  of  amorphous  globules  termed  "fuchsin-bodies," 
because  they  stain  darkly  with  this  dye.  Now  fuchsin- 
bodies  are  found  in  the  olfactory  apparatus  of  the  brain, 
after  it  has  begun  to  atrophy,  and  there  can  be  no  doubt 
that  they  indicate  cells,  or  blood,  which  have  undergone 
chemical  change.  The  nests  of  epithelial  cells  are  probably 
the  remains  of  gland  tissue  —  blocked-up  ducts,  we  may 
say,  almost  with  certainty  after  studying  the  development  of 
the  body.  Here,  then,  is  an  organ  which  grows  like  a 
gland  (or  like  an  organ  of  respiration),  although  it  is  not 
found  as  a  functional  gland  in  any  vertebrate.  \Yhat  is  it 
doing  in  Man  ?  It  is  a  manuscript  which  cannot  be  read. 
The  characters  in  which  it  is  written  were  obsolete  before 
the  earliest  fish  came  into  existence.  Why,  then,  has  it  been 
retained?  For  the  sake  of  the  palimpsest,  which  we  can 
read.  Like  all  other  glands  formed  in  connection  with  the 
front  part  of  the  alimentary  canal,  it  is  surrounded  by 
lymphoid  tissue.  For  the  sake  of  this  crossed  writing  it  is 
retained  in  every  individual  until  he  reaches  an  age  at  which 
his  great  need  of  a  nursery  for  young  leucocytes  has  les- 
sened. After  that  it  disappears. 

It  is  not  only  in  living  things  as  they  appear  in  the  adult 
condition  that  the  biologist  traces  adaptation,  now  that  the 
law  of  evolution  has  been  formulated,  but  in  every  stage  of 
growth.  As  he  watches  the  changes  through  which  the 
single-celled  ovum  evolves  into  the  fully  grown  animal,  he 
sees  the  race  of  which  this  particular  species  is  the  heir 
passing  through  all  the  stages  which  have  marked  its  his- 
tory from  age  to  age.  In  a  few  days,  or  weeks,  or  months, 
a  drama  is  acted  which  it  has  taken  geological  seons  to 
rehearse,  for  every  individual  recapitulates  in  its  growth  the 
successive  stages  to  which  its  ancestors  attained,  and  at 


ORIGIN   OF    SPECIES  95 

which  they  severally  stopped.  What  explanation  could  the 
teacher  of  fifty  years  ago  give  of  the  gill-slits,  or  tail,  or  a 
hundred  other  resemblances  to  lower  vertebrates  which  the 
human  embryo  presents  in  the  course  of  its  development  ? 
They  are  by  no  means  necessary  preparations  for  adult 
structure.  They  never  can  be  useful.  Not  infrequently 
they  are  mischievous.  Indeed  Man's  organs  reach  their 
permanent  form  by  many  a  roundabout  road.  These 
digressions  are  indications  of  the  tenacity  of  Nature's 
memory.  She  can  attain  her  goal  only  by  tracing  over 
again  —  with  a  jump  here  and  a  short  cut  there  it  may  be, 
but  without  letting  go  of  the  clue  —  the  path  which  she 
followed  when  she  first  discovered  it. 

We  are  now  in  a  position  to  understand  the  influence 
which  Darwin's  theorem  has  had  upon  the  taxonomist.  It 
is  no  longer  enough  that  he  should  classify  living  things 
according  to  their  natural  affinities  —  he  must  group  them 
according  to  their  proximity  to  one  another  on  the  ancestral 
tree.  His  classes  are  the  several  stems  of  this  tree,  his 
orders  its  main  branches.  Its  small  branches  are  genera 
and  its  twigs  species.  Their  "natural  affinities"  do,  of 
course,  indicate  relationship,  but  the  taxonomist  must  be- 
ware of  mere  resemblances.  He  can  only  be  sure  that  he 
has  traced  their  pedigree  when  he  finds  two  extant  forms 
uniting  —  losing  their  differences  —  in  a  fossil  ancestor.  The 
geological  record  is,  however,  so  imperfect  that  it  is  but 
seldom  that  certainty  can  be  claimed. 

In  any  attempt  at  classifying  animals  a  great  and  hitherto 
impassable  gap  is  found  between  invertebrates  and  verte- 
brates. There  is,  as  it  were,  a  wedge-shaped  blank  in  the 
picture  of  the  ancestral  tree.  Evidently  a  vast  number  of 
intermediate  forms  have  died  out,  leaving,  according  to  the 
common  reading  of  the  rock-record,  no  trace  behind. 
When  the  highest  of  the  invertebrates  of  the  epoch  at  which 
the  change  occurred  began  to  assume  what  is  now  known 
as  the  vertebrate  type,  its  transitional  form  cannot  have 


96  AN   INTRODUCTION    TO    SCIENCE 

favoured  it  much  in  the  struggle  for  existence.  Of  its  suc- 
cessors but  few  survived,  and  these  only  such  species  as 
inclined  strongly  towards  the  vertebrate  type.  The  new 
type  was,  therefore,  established  with  comparative  rapidity. 
But  when  once  it  had  acquired  something  like  permanent 
character  this  form  of  animal  showed  that  it  could  not  only 
hold  its  own  against  invertebrates,  but  that  it  contained  a 
potentiality  for  development  into  "a  great  nation."  It  is 
difficult  to  imagine  the  conditions  which  favoured  this 
remarkable  transition.  Probably  it  is  better  not  to  try. 
The  facts  remain  that,  whereas  it  can  be  proved  from  em- 
bryological  evidence  that  the  vertebrate  had  an  invertebrate 
ancestor,iand  whereas  the  difference  between  the  two  types 
is  of  the  most  pronounced  kind,  zoologists  are  not  agreed 
that  any  indubitably  intermediate  forms  have  been  found, 
either  extant  or  extinct. 

Anyone  who  has  taken  the  facts  above  stated  into  con- 
sideration will  anticipate  a  bold  theory  of  the  transition  from 
an  invertebrate  to  a  vertebrate  type,  but  the  more  he  dwells 
upon  the  essential  differences  between  the  two  the  more 
clearly  will  he  see  that  only  a  bold  theory  can  hope  to 
justify  itself.  The  most  striking  differences  are  these  :  The 
vertebrate  has  a  backbone  which  gives  off  two  series  of  bony 
arches,  the  one  dorsal  (the  vertebral  arches)  to  enclose  the 
spinal  cord,  the  other  ventral— jaws,  hyoid  arch  and  ribs — 
to  enclose  the  alimentary  canal  and  viscera.  When  an  in- 
vertebrate has  a  skeleton  it  is  usually  external,  like  the 
calcareous  case  of  a  lobster,  for  example.  The  vertebrate 
central  nervous  system  (brain  and  spinal  cord)  lies  entirely 
on  the  dorsal  side  of  the  vertebral  column,  and  therefore  on 
the  dorsal  side  of  the  alimentary  canal.  The  central  nervous 
system  of  an  invertebrate  is  partly  dorsal,  partly  ventral.  In 
the  octopus,  for  example,  which  (with  the  exception  of 
spiders  and  scorpions,  perhaps)  has  the  nearest  approach  to 
a  brain  found  in  any  invertebrate,  the  nervous  ganglia  are 
collected  into  a  group,  enclosed  by  a  rudimentary  cartilagi- 


ORIGIN    OF    SPECIES  97 

nous  skull,  which  is  pierced  by  the  gullet.    The  gullet  goes 
straight  through  the  middle  of  the  skull  and  brain. 

We  have  said  that  the  vertebrate  passes  through  inverte- 
brate stages  during  its  early  growth,  or,  in  other  words,  that 
both  vertebrate  and  invertebrate  pass  through  the  same 
stages  up  to  a  certain  date.  They  may  in  a  few  words  be 
described  as  follows :  First,  the  one-celled  ovum  divides 
into  a  "mulberry  mass."  This  mass  next  becomes  a  hollow 
sphere.  One  side  of  the  ball  is  then  pitted  in,  so  that  a  cup 
(the  gastrula)  is  made,  lined  by  a  sheet  of  cells,  the  endo- 
derm,  covered  by  a  sheet  of  cells,  the  ectoderm.  But  little 
change  is  needed  to  make  such  an  embryo  into  a  sea- 
anemone.  The  endoderm  is  its  stomach  ;  the  ectoderm,  its 
body- wall ;  the  space  between  them,  its  body  cavity.  With 
a  fringe  of  tentacles  round  the  mouth  it  is  practically  com- 
plete. Now,  however  great  may  be  the  elaboration  of  this 
type  in  invertebrates,  its  main  features  remain  the  same  ; 
the  hole  left  by  the  pitting  in  is  the  mouth  ;  the  nervous 
system  is  formed  as  a  circle  round  this  hole.  The  first 
difficulty  in  continuing  the  line  from  the  invertebrate  to  the 
vertebrate  sub-kingdom  is  met  with  when  we  try  to  recog- 
nise these  early  stages  in  the  latter.  The  vertebrate  also 
shows  a  pitting-in,  the  "primitive  trace"  and  blastopore, 
followed  by  an  lip-growth  of  the  "medullary  folds,"  the 
walls  of  which  grow  into  the  brain  and  spinal  cord.  If  this 
corresponds  to  the  pitting-in  to  form  the  stomach  of  the 
gastrula,  it  follows  that  in  vertebrates  a  new  stomach  has 
been  acquired  ;  while  the  old  stomach  has  become  the  ven- 
tricles of  the  brain  and  the  central  canal  of  the  spinal  cord. 
How  has  the  new  alimentary  canal  been  formed  ?  Verte- 
brate embryos  (and  many  invertebrate  embryos  also)  are 
provided  with  a  store  of  food  -the  yolk.  For  the  purpose 
of  tapping  this  supply  of  food  a  diverticulum  grows  out  from 
the  hinder  end  of  the  neur-enteric  canal.  This,  according  to 
the  view  just  enunciated,  becomes  in  vertebrates  the  per- 
manent alimentary  canal.  But  It  has  no  opening  to  the 


98  AN    INTRODUCTION    TO    SCIENCE 

exterior  ;  and  the  phenomenon  which  all  zoologists  have  had 
to  try  to  explain  is  the  formation  of  a  new  mouth  which 
occurs  at  the  anterior  end  of  the  vertebrate  embryo,  perfo- 
rating through  into  the  so-called  fore- gut. 

Taking  the  widest  view  of  these  and  of  many  other 
differences  in  structures  which  distinguish  the  vertebrate 
from  the  invertebrate,  Dr.  Gaskell  has  offered  us  a  startling 
explanation  of  the  transformation  which  has  occurred.  All 
those  parts  of  the  invertebrate  body  which  are  median  and 
impaired — all  that  makes  up  the  body  of  the  sea-anemone, 
that  is  to  say,  but  not  the  limbs  of  insects,  lobsters,  and 
other  bilaterally  symmetrical  animals — lie  on  the  dorsal 
side  of  the  vertebral  column.  Its  invertebrate  alimentary 
canal  is  our  neural  canal.  Its  stomach  is  the  ventricular 
cavity  in  our  brain — its  gullet  passed  through  a  hole  (the 
pituitaiy  fossa)  in  the  base  of  our  skull.  Every  anatomist 
recognises  that  the  central  nervous  system  is  the  most  con- 
servative system  in  the  body.  It  is  the  first  part  to  be 
formed  in  the  embryo,  the  last  to  follow  the  changes  in 
other  organs  of  the  body.  Nerves  may  change  their  course, 
but  their  centres  in  the  cerebro-spinal  axis  remain  unaltered. 
The  whole  animal  may  alter  in  appearance,  but  the  nervous 
system  is  not  essentially  affected.  It  is  the  central  system 
about  which  the  rest  of  the  body  grows ;  and  there  can  be 
little  doubt  that  the  central  nervous  organs  in  man  are 
homologous  with  those  of  arthropods  or  molluscs,  little  as 
any  other  part  of  our  body  finds  its  counterpart  in  these 
animals.  In  the  invertebrate  the  central  nervous  system 
consists  of  a  collar  round  the  oesophagus,  certain  ganglia  in 
the  head,  and  a  double  chain  of  ganglia  along  the  ventral 
side  of  the  alimentary  canal.  These  ganglia,  says  Dr. 
Gaskell,  which  have  already  coalesced  in  the  highest  inver- 
tebrates, become  the  brain  and  spinal  cord.  Growing  vastly 
in  importance  as  the  animal  series  is  ascended,  they  have 
grown  round  and  blocked  in  its  primitive  alimentary  canal. 

If  we  wish  to  trace  the  history  of  the  greater  part  of  our 


ORIGIN    OF    SPECIES  99 

body,  we  must  understand  that  there  has  been  a  great  shift- 
ing of  functions  among  the  organs.  The  stomach,  the  liver, 
and,  in  a  certain  sense,  the  lungs  are  new.  Indeed  our 
thyroid  body — the  two  lobes  at  the  side  of  the  larnyx, 
which  sometimes  hypertrophy  into  goitre,  an  organ  of 
which  hitherto  neither  anatomists  nor  physiologists  have  been 
able  to  give  an  explanation  —  is  a  disused  reproductive  organ 
of  our  invertebrate  ancestors.  Our  two  eyes  may  be  repre- 
sented in  the  ocelli  and  lateral  eyes  of  some  invertebrates, 
but  they  are  not  their  median  eyes.  The  eye  of  an  octopus 
looks  very  much  like  that  of  a  fish,  but  it  has  long  been 
known  that  it  is  constructed  on  quite  a  different  plan.  In 
the  eye  of  the  octopus  the  rods  and  cones,  the  elongated 
cells  which  are  sensitive  to  light,  are  directed  forwards ; 
in  the  fish  they  are  directed  backwards,  and  the  front  of 
the  retina  consists  of  a  sheet  of  transparent  nerve  fibres. 
The  eye  of  the  vertebrate  is,  therefore,  the  invertebrate 
eye  turned  inside  out.  Ingenious  hypotheses  have  been 
formulated  to  explain  how  this  puzzling  involution  came 
about.  There  is  no  need  of  any  hypothesis,  according  to 
Dr.  Gaskell.  Deeply  seated  in  the  centre  of  our  brain  is 
a  little  conical  organ,  the  pineal  body,  which  has  acquired 
a  spurious  fame,  because  Descartes,  looking  at  it  in  its 
relation  to  the  great  hemispheres  of  the  brain  and  the 
cerebellum  which  overarch  it,  and  thinking  how  closely  it 
resembled  an  organist  seated  at  an  organ,  imagined  that  it 
might  be  the  seat  of  the  soul.  The  pineal  body  in  certain 
curiously  archaic  reptiles,  particularly  Hatteria  punctata  of 
New  Zealand,  has  a  long  stalk  and  reaches  to  a  hole  in  the 
roof  of  the  skull,  which  is  closed  by  semi-transparent  mem- 
brane, and  in  structure  it  is  most  clearly  an  eye  formed  on 
the  invertebrate  plan.  Hatteria  has  two  inverted  eyes,  as  we 
may  call  them,  as  well  as  its  cyclopean  pineal  eye  in  the 
middle  of  its  head  ;  but  Dr.  Gaskell  has  shown  from  its 
development  in  the  larva  of  the  lamprey,  that  the  pineal  eye 
was  formerly  paired,  and  that  its  connections  with  the  brain 


TOO  AN   INTRODUCTION    TO    SCIENCE 

are  similar  to  those  of  the  median  eyes  of  invertebrate  ani- 
mals. Lastly,  to  touch  upon  the  question  of  the  new  mouth 
of  vertebrates  :  the  anterior  part  of  the  new  gut  was  originally 
a  respiratory  chamber,  which  afterwards  served  as  an  ali- 
mentary canal.  This  respiratory  chamber  was  formed,  as 
it  is  now  formed  in  the  scorpion  group,  by  the  insinking  of 
respiratory  apparatus,  which  in  other  arthropods,  such  as  lob- 
sters, stand  out  on  the  under  side  of  the  head.  Indeed  the 
nearest  approach  which  we  can  make  to  picturing  our  ances- 
tor in  the  direct  line  at  the  point  at  which  the  vertebrate  and 
the  invertebrate  sub-kingdoms  branched  off,  is  to  represent 
him  as  resembling  one  of  the  old  extinct  sea-scorpions ;  and 
the  earliest  animal  for  which  we  can  find  a  place  in  our 
pedigree  after  the  separation  took  place  is  the  earliest  known 
fish  thycotis,  which  is  found  in  Upper  Silurian  strata.  This 
fish  belongs  to  a  long  extinct  group,  the  cephalaspids,  which 
present  many  points  of  resemblance  with  the  lowest  of  exist- 
ing fishes,  the  lamprey  in  its  larval  stage  ;  while,  on  the 
other  hand,  they  show  many  indications  of  kinship  with  the 
trilobites  and  old  sea-scorpions. 

Dr.  Gaskell's  views,  which  he  has  advocated  with  great 
persistency  and  ingenuity,  have  been  much  discussed  at 
recent  meetings  of  the  British  Association  and  other  scien- 
tific societies.  The  majority  of  zoologists  are  opposed  to 
them,  but,  even  if  it  were  otherwise,  it  would  be  going  be- 
yond our  province  to  express  an  opinion  upon  any  hypothesis 
which  is  still  under  discussion.  We  wish  to  introduce  the 
reader  to  the  problems  which  are  occupying  the  attention  of 
scientific  men  without  prejudicing  his  judgement ;  and 
certainly  no  more  striking  illustration  of  the  profound  change 
which  Darwin's  doctrine  has  effected  in  biological  thought 
could  be  cited.  This  missing  chapter  in  the  history  of  the 
animal  kingdom  has  to  be  written,  but  no  one  thirty  years 
ago  would  have  ventured  on  so  bold  a  rendering. 

The  biologist  first  observes  and  collects.  He  then 
classifies,  empirically  to  begin  with,  but  according  to  prin- 


ORIGIN    OF    SPECIES  101 

ciple  later  on.     When  he  surveys  the  ^immense  variety  cf 
animals  and  plants,  the  question  naturally' .presents  itseJf^to 
his  mind,  Why  so  many?    How'  did  this  vast  array  come  , 
into  existence ?  ^    ^  //,  *      ',  i»  •'   *  Uf  ;'•,;  i 

Certain  facts  are  quite  clear.  The  conditions  which  have 
obtained  on  the  globe  since  first  it  was  habitable  by  living 
things  have  undergone  great  progressive  changes.  They 
have  also  fluctuated  from  time  to  time.  Plants  or  animals 
which  could  live  upon  the  earth  or  upon  a  particular  part  of 
the  earth  in  one  geological  epoch  would  have  been  killed 
off  in  the  next.  Fossil-forms  make  their  appearance  and 
disappear  in  successive  strata.  As  stratum  follows  upon 
stratum  the  number  and  variety  of  fossils  increases,  and  the 
specialization  of  their  structure  also  increases  progressively 
from  period  to  period. 

No  one  who  knows  these  facts  can  fail  to  draw  the 
conclusion  that  transmutation  of  species  in  the  direction  of 
improvement  or  evolution  has  occurred.  The  question 
which  biologists  are  debating  at  the  present  time  is,  What 
is  the  cause  of  evolution  ? 

Lamarck  recognised  that  the  conditions  of  life,  the  envi- 
ronment, cause  changes  in  the  individual.  He  supposed 
that  these  changes,  being  transmitted  to  the  offspring,  lead 
to  progressive  transmutation. 

Darwin  laid  stress  upon  the  fact  that  in  the  struggle  for 
existence  Nature  encourages  only  the  more  fit.  As  all  but 
the  more  fit  die  out  without  reproducing  their  kind,  the 
fitness  of  the  species  which  survive  progressively  increases. 

The  great  question  now  at  issue  is  :  What  is  the  cause  of 
the  initial  variation  which  gives  to  Nature  a  diversity  of 
material,  less  fit,  equally  fit,  and  more  fit,  from  which  to 
select  ? 

The  only  explanation  of  variation  is  based  upon  the 
"  Lamarckian  factors,"  or  the  proposition  that  the  increased 
growth  which  use  induces  is  transmitted  by  a  parent  to  its 
offspring.  Improvement  is,  from  this  point  of  view,  the 


102  AN  INTRODUCTION    TO  SCIENCE 

.direct  effect  tof\  environment,  since  acquired  characters  are 


But  Wallace,   Weissmann    and    most    post-Darwinians 
'  accept,  thjs  theorem.     Some  take  the  a  priori 


'  ground  that  trie  transmission  of  acquired  characters  is 
incomprehensible.  Reproduction  means,  as  they  point  out, 
that  the  parent  divides  into  two  parts,  one  so  large  as  to  be 
practically  unaffected  by  the  division  ;  the  other  a  minute 
cell,  the  ovule  in  a  carpel,  the  pollen  grain  in  an  anther  or 
the  corresponding  cells  in  the  two  sexes  of  animals.  Is  it 
conceivable,  they  ask,  that  the  whole  of  the  male  parent, 
with  his  acquired  peculiarities,  is  mirrored  in  his  "  gamete," 
and  the  whole  of  the  female  in  hers?  Other  biologists 
decline  to  accept  the  doctrine  of  the  transmission  of 
acquired  characters,  on  the  ground  that  such  transmission 
has  never  been  proved  under  any  conditions  we  are  able  to 
arrange,  or  within  any  period  of  time  over  which  observa- 
tions extend.  We  have,  for  example,  instances  of  the 
mutilation  of  thousands  of  successive  generations  without 
any  tendency  towards  the  diminution  of  the  organ  removed. 
Every  cur's  puppy  flourishes  a  tail  —  does  its  best  to  rise  to 
the  dignity  of  a  dog  —  centuries  after  the  passing  of  a  law 
that  all  except  the  dogs  of  the  nobility  who  enjoyed  sport- 
ing rights,  should  be  curtailed  {court  taille}.  But  for 
reasons  into  which  we  cannot  enter  the  evidence  from 
mutilation  is  by  some  biologists  (by  Darwin  himself)  ruled 
out  of  court. 

The  adaptation  of  the  individual  to  his  environment  is  a 
matter  of  experience.  A  blacksmith's  biceps  are  bigger 
than  those  of  a  clerk.  A  seed  sown  in  a  new  soil  and  under 
a  new  climate  produces  a  plant  different  in  many  respects 
from  its  parent.  But  are  these  peculiarities  transmitted  to 
offspring?  If  it  could  be  shown  that  the  seeds  of  the  trans- 
ported plant,  when  sown  in  the  original  habitat  of  the 
species,  produce  plants  which  are  unlike  their  wild  neigh- 
bours (in  respects  which  cannot  be  accounted  for  by  sup- 


ORIGIN    OF    SPECIES  103 

posing  that  the  seeds  have  stored  more  food  materials,  or 
less,  than  they  would  have  stored  in  their  original  habitat), 
the  inheritance  of  acquired  characters  would  be  proved. 
Unfortunately,  if  we  give  the  plants  a  few  generations  in 
which  to  render  their  new  features  pronounced,  we  give 
time  for  "natural  selection"  to  obscure  the  result. 

The  alternative  to  the  doctrine  of  the  inheritance  of 
acquired  characters  is  not  an  explanation  but  a  statement, 
although  it  may  be  qualified  by  various  mediate  theories  of 
"germ-plasm,"  "heredity,"  etc.  It  is  pointed  out,  as  a 
matter  of  common  observation,  that  when  two  "gametes" 
have  fused  into  a  "zygote,"  this  fertilized  cell  grows  into 
an  individual  which  reproduces  neither  of  its  parents  with 
exactness,  nor  is  it,  so  to  speak,  the  mean  of  the  two. 
Variation  is  therefore  a  fact,  whatever  may  be  its  cause,  and 
since  but  a  small  fraction  of  all  the  zygotes  produced 
develop  into  plants  or  animals  capable  of  reproducing  in 
their  turn,  nature  eliminates  all  but  favourable  variations. 
Of  the  variability  of  the  zygotes  we  know  nothing.  We  only 
know  that  the  individuals  into  which-  they  develop  vary. 
We  cannot  say  whether,  if  the  conditions  as  to  supply  of 
food  and  incidence  of  external  forces  were  identical,  the 
individuals  would  be  identical,  because  such  absolute  iden- 
tity of  conditions  is  unattainable.  We  only  know  that  the 
zygotes  contain  a  potentiality  of  variability,  which,  after  all, 
comes  to  the  same  thing. 

The  "New  Darwinism"  has  given  rise  to  an  extensive 
literature,  and  many  proximate  theories,  or  rather  formu- 
laries, have  been  enunciated,  but  the  main  problem  is  still  un- 
solved. The  doctrine  of  Natural  Selection  declares  that  fa- 
vourable variations  are  perpetuated.  The  explanation  which 
is  usually  styled  "Lamarckian"  gives  as  the  cause  of  vari- 
ation the  tendency  of  the  offspring  to  inherit,  in  a  more  or 
less  pronounced  degree,  the  characters  acquired  by  its  par- 
ents. Weissmannism  makes  a  tendency  to  vary  an  essential 
quality  of  germ-plasm,  but  gives  no  explanation  of  its  cause. 


104  AN    INTRODUCTION    TO    SCIENCE 

When  the  question  is  looked  at  in  its  broadest  aspects  it 
is  evident  that  since  the  world  became  habitable  the  condi- 
tions of  existence  have  undergone  incessant  change.  Liv- 
ing things  have  changed.  Collectively,  they  have  continu- 
ously adapted  themselves  to  their  environment.  Therefore, 
whatever  may  be  the  proximate  cause  of  their  variability,  it 
is  ultimately  due  to  the  action  of  the  environment. 


CHAPTER  VI 

The   Cause    of  the   Coagulation   of  the  Blood : 
A  Problem  in  Physiology 

IF  the  state  of  development  of  a  science  may  be  judged 
by  the  amount  of  literature  to  which  it  has  given  rise,  with- 
out regarding  its  accuracy  either  in  fact  or  inference,  Physi- 
ology attained  to  considerable  proportions  even  among  the 
Egyptians,  which  would  place  it  among  the  oldest  of  the 
sciences.  If,  on  the  contrary,  the  development  of  a  science 
varies  as  the  truth  of  its  data  and  the  finality  of  its  theories, 
Physiology  is  modern  indeed,  and  has  much  progress  still  to 
make.  It  is  not  to  be  wondered  at  that  the  working  of 
the  animal  body  has  at  all  times  occupied  the  thoughts  of 
philosophers. 

Physiology  differs  from  most  other  branches  of  science  in 
that  it  has  no  predominant  problems.  For  ages  its  votaries 
were  engaged  in  a  vague  quest  for  the  Principle  of  Life,  but 
as  knowledge  increased  it  was  realised  that  the  phenomena 
exhibited  by  a  living  thing  are  in  every  respect  comparable 
to,  are  indeed  the  results  of,  the  action  of  forces  in  the 
world  outside  the  body.  The  doctrine  of  Vitalism  has  been 
abandoned.  No  longer  does  the  physiologist  seek  for  any 
wide  generalization  which  shall  illuminate  every  department 
of  his  subject.  He  recognises  that  as  the  body  consists  of 
many  organs,  each  organ  of  tissues,  and  every  tissue  of  cells, 
he  has  before  him  a  vast  number  of  problems  all  of  equal 
importance  to  the  complete  understanding  of  the  mechanism 
of  the  living  body. 

(105) 


lo6  AN    INTRODUCTION    TO    SCIENCE 

We  may  select  as  illustrations  of  the  methods  of  the 
science  two  problems  of  different  orders:  (i)  the  cause 
of  the  coagulation  of  the  blood  ;  (2)  the  nature  of  the 
control  which  the  nervous  system  exerts  over  the  body. 
Contributions  towards  the  solution  of  these  problems  have 
been  made  by  the  naturalists  of  all  ages,  although  it  still 
remains  for  the  scientific  workers  of  the  future  to  discover 
facts  which  must  be  added  to  the  chain  of  evidence  before 
the  final  verdict  is  given.  The  history  of  these  problems 
illustrates  in  a  striking  way  the  natural  growth  of  Science. 

That  blood  clots  a  few  minutes  after  it  is  shed  is  an 
observation  which  could  not  fail  to  attract  the  attention  of 
primitive  man.  The  more  primitive  the  man,  the  more 
numerous  were  the  opportunities  which  he  enjoyed  of  ob_ 
serving  this  phenomenon. 

Why  does  blood  clot  when  out  of  the  body,  and  why  does 
it  not  clot  while  it  remains  within  the  blood-vessels? 

Aristotle  knew  the  immediate  cause  of  coagulation  ;  that 
it  is  due  to  the  formation  of  fibrin  (or  fibres,  as  he  called 
them),  and  his  explanation  of  why  the  fibres  form  was  a 
natural  one,  although  the  very  reverse  of  the  true  explana- 
tion, as  we  shall  see.  "Coagulation  occurs  in  the  earthy 
part  of  the  blood,  that  is,  in  the  fibres,  during  the  evaporation 
of  the  moisture."  "  If  the  fibres  are  removed  from  the  blood 
of  a  bull" — if  it  is  whipped  with  a  bundle  of  twigs  so  that 
the  fibres  are  collected  on  the  twigs— "the  blood  will  not 
clot."  "If  the  fibres  be  left  the  fluid  coagulates,  as  does 
also  mud,  under  the  influence  of  cold.  For  when  the  heat 
is  expelled  by  the  cold,  the  fluid,  as  has  been  already  stated, 
passes  off  with  it  by  evaporation,  and  the  residue  is  dried  up 
and  solidified,  not  by  heat  but  by  cold.  So  long,  however, 
as  the  blood  is  in  the  body  it  is  kept  fluid  by  animal  heat."  * 
To  the  idea  of  the  escape  of  heat  which  was  set  forth  in 


*  "On  the  Parts  of  Animals,"  Book  ii.,  Chap.  iv.    Dr.  Ogle's  trans- 
lation. 


COAGULATION   OF   THE   BLOOD  107 

great  detail  by  Aristotle  because  he  believed  that  the  process 
of  coagulation  resembled  the  setting  of  a  solution  of  gelatin, 
was  subsequently  added  the  explanation  that  the  blood  is 
kept  from  coagulating  as  long  as  it  is  in  a  state  of  motion, 
but  clots  when  it  comes  to  rest.  What  explanation  could  be 
more  natural  ?  The  soldier  was  found  on  the  battlefield 
lying  in  a  pool  of  blood  which  had  come  to  rest,  grown 
cold,  and  coagulated.  The  clotting  was  due  to  cold  and 
rest. 

This  was  the  accepted  explanation  until  the  middle  of  the 
last  century.  Indeed,  it  held  its  own  until  much  later,  not- 
withstanding Hewson's  demonstration  of  its  insufficiency. 
In  jnedical  writings  of  the  eighteenth  century  we  constantly 
meet  with  the  statements  that  "Blood  coagulates  when  ex- 
posed to  a  moderate  degree  of  cold."  "  Blood  coagulates 
when  it  is  deprived  of  the  attrition  to  which  it  is  exposed 
when  circulating  within  the  vessels  of  the  body."  Such  neg- 
ative statements  are  unexceptionable.  But  we  also  meet 
with  positive  assertions  which  certainly  were  not  based  upon 
experience.  "The  blood  will  not  coagulate  if  the  cup  into 
which  it  is  received  be  kept  at  the  temperature  of  the  body." 
"If  the  blood  be  kept  in  motion  by  rapid  stirring  with  a 
glass  rod  it  is  hindered  from  setting  a  clot."  It  would  seem 
to  us,  with  our  modern  axiom  "  Check  your  references,"  to 
have  been  easy  to  put  such  assertions  to  the  test :  especially 
easy  in  the  days  when  the  traditions  of  his  profession  directed 
a  surgeon  to  let  blood  in  almost  every  case  he  attended,  as 
an  obviously  remedial  measure  which  he  might  safely  adopt 
before  he  proceeded  to  inquire  as  to  what  was  amiss  with 
the  patient.  But  these  statements  were  not  based  upon  ob- 
servation. They  illustrate  a  very  different  method  which  was 
more  commonly  pursued  by  the  medical  writers  of  that  time. 
Accepting  the  authority  of  Aristotle  and  his  successors  as 
unquestionable,  they  argued  that  if  blood  coagulates  when  it 
leaves  the  body,  because  it  grows  cold  and  comes  to  rest,  it 
follows  that  it  will  not  coagulate  if  it  is  kept  warm  and  in 


loS  AN  INTRODUCTION    TO    SCIENCE 

motion.    This  conclusion  being  unassailable,  they  stated  the 
phenomena,  which  they  knew  must  hold  good,  as  facts. 

William  Hewson,  "F.  R.  S.  and  Teacher  of  Anatomy," 
commenced,  in  1767,  a  series  of  experiments  which  he 
published  under  the  title  of  "An  Inquiry  into  the  Properties 
of  the  Blood."  His  methods  are  admirable,  and  his  con- 
clusions are  drawn  with  the  modesty  which  should  always 
characterize  scientific  thought.  "Two  of  the  latest  writers 
on  this  subject  agree  that  if  fresh  blood  be  received  into  a 
cup,  and  that  cup  put  into  water  heated  to  98°,  it  will  not 
separate  ;  nay,  they  even  say  that  it  will  not  coagulate  ;  but 
this,  I  am  persuaded  from  experiments,  is  ill-founded."* 
After  reciting  experiments  which  showed  that  blood  kept  at 
the  body  temperature,  as  nearly  as  his  apparatus  allowed, 
coagulated  even  sooner  than  the  same  blood  left  exposed  to 
the  temperature  of  the  air,  he  proceeds  to  put  the  matter  to 
a  crucial  test.  He  ligatures  a  vein  in  the  neck  of  a  dog  in 
two  places  and  then  covers  it  with  the  skin  to  prevent  its 
cooling.  Opening  the  vein  after  an  interval  he  found  the 
blood  in  it  coagulated,  although  coagulation  was  very  con- 
siderably delayed.  In  this  experiment  the  blood  was  kept 
warm,  but  it  was  allowed  to  come  to  rest.  "  Blood,  when 
received  into  a  basin  very  soon  jellies  or  coagulates.  The 
circumstances  in  which  it  now  differs  from  what  it  was  in 
the  veins  are  these  :  it  is  exposed  to  the  air,  to  cold,  and  is 
at  rest.  The  question  is,  to  which  of  these  circumstances 
its  coagulation  whilst  in  the  basin  is  chiefly  owing.  As  the 
subject  seemed  to  me  of  importance,  I  have  endeavoured  to 
ascertain  the  circumstance  to  which  this  coagulation  is 
owing  by  several  experiments,  in  each  of  which  the  blood 
was  generally  exposed  to  but  one  of  the  suspected  causes  at 
a  time."  He  repeats  the  experiment  of  ligaturing  the  vein 
in  two  places.  "From  several  experiments  made  in  this 


*  "  An  Experimental    Inquiry   into   the   Properties   of  the   Blood," 
second  edition,  p.  3,  1772. 


COAGULATION   OF   THE  BLOOD  109 

way,  I  found  in  general  that  after  being  at  rest  for  ten 
minutes,  the  blood  continued  fluid  ;  nay,  that  after  being  at 
rest  for  three  hours  and  a  quarter,  above  two-thirds  of  it 
were  still  fluid,  though  it  coagulated  afterwards.  Now  the 
blood  when  taken  from  a  vein  of  the  same  animal  was 
completely  jellied  in  about  seven  minutes.  The  coagulation 
-  of  the  blood  in  the  basin  and  of  that  which  is  at  rest  are  so 
different  that  rest  alone  cannot  be  supposed  to  be  the  cause 
of  the  coagulation  out  of  the  body."  This  is  not  clearly 
expressed,  but  it  evidently  means  that  were  rest  the  sole 
cause  of  coagulation  the  blood  at  rest  in  the  vein  would 
have  coagulated  as  quickly  as  the  blood  in  the  basin.  We 
cannot  follow  Hewson  further  in  his  investigations.  He  cuts 
out  the  ligatured  vein  and  freezes  it  and  shows  that  after  it 
has  been  thawed  it  is  still  fluid  and  still  ready  to  coagulate. 
He  places  the  excised  vein  in  water,  which  he  warms  to 
various  temperatures,  and  finds  that  it  is  not  immediately 
coagulated  at  114°  Fahr.,  although  it  is  at  120°  Fahr.  And 
lest  this  result  should  be  regarded  as  a  heat-coagulation, 
such  as  occurs  when  a  solution  of  white  of  egg  is  heated, 
and  not  the  natural  process,  ' '  It  may  be  necessary  to  ob- 
serve here  that  the  part  coagulated  was  only  the  lymph 
(plasma) ;  for  the  serum  requires  a  much  greater  heat  to  fix 
it,  that  is,  a  heat  of  160°,  as  will  appear  hereafter."  Hew- 
son's  methods  closely  resemble  those  of  his  contemporaries 
William  and  John  Hunter,  Henry  Cavendish,  Antoine 
Laurent  Lavoisier.  We  have  given  these  few  extracts 
from  Hewson's  book  in  his  own  words  because  they  show 
how  thoroughly  he  was  embued  with  the  great  principle 
which  may  be  said  to  have  dawned  upon  Science  at  this 
period,  supplying  a  code  of  rules  to  the  observance  of 
which  all  subsequent  advance  was  due — the  principle  of 
the  control  experiment.  He  arranged  that  only  one  of  the 
suspected  causes  should  act  at  a  time,  and  he  had  the 
scientific  insight  which  warned  him  that  one  experiment 
under  natural  conditions  was  better  than  a  hundred  in 


no  AN  INTRODUCTION    TO    SCIENCE 

which  all  the  conditions  are  artificial.  Had  Hewson  exam- 
ined the  blood  only  after  it  was  drawn  from  the  body,  he 
would  have  placed  it  in  contact  with  a  china  or  metal  cup, 
would  have  exposed  it  to  air  and  to  dust,  would  have 
allowed  its  halitus  or  volatile  spirit  to  escape,  and  in  many 
other  respects  he  would  have  introduced  conditions  any  one 
of  which  he  might  have  mistaken,  as  they  all  were  mistaken 
by  his  successors,  as  the  vera  causa  of  coagulation. 

Whence  does  the  fibrin  come  ?  What  is  its  condition  in 
circulating  blood?  Prevost  and  Dumas  (1823)  studied  the 
chemical  properties  of  fibrin,  and  decided  correctly  that  it 
could  not  be  in  a  condition  of  solution  in  circulating  blood. 
It  is  not  a  soluble  substance.  They  also  observed  under  the 
microscope  that  multitudes  of  globules,  resembling  the 
nuclei  of  blood- corpuscles,  were  entangled  in  the  clot,  and 
they  inferred  that  the  fibrin  was  present  in  the  blood  as 
fibrin,  but  was  in  some  way  fixed  to,  or  formed  part  of,  the 
corpuscles.  Their  description  is  not  sufficiently  clear  to 
enable  one  to  say  exactly  what  was  their  idea  of  the  relation 
of  the  fibrin  to  the  corpuscles.  "The  attraction  which 
keeps  the  red  matter  fixed  around  the  white  globules 
having  ceased  along  with  the  motion  of  the  fluid,  these 
globules  are  left  at  liberty  to  obey  the  force  which  tends  to 
make  them  combine  and  form  a  network,  in  the  meshes  or 
around  the  plates  of  which  the  colouring  matter  is  included 
along  with  a  great  quantity  of  particles  which  have  escaped 
this  spontaneous  decomposition."*  Milne-Edwards  tells 
us  that  "this  theory  has  been  adopted  by  the  greater 
number  of  the  physiologists  of  the  present  day."f  For  his 
own  part,  however,  he  considered  that  the  fibrin  "is  merely 
suspended  in  the  mass  of  the  blood  in  a  state  of  extreme 
subdivision,  and  possessed  of  transparency  too  perfect  to 
admit  of  its  being  seen  amidst  the  surrounding  fluid." 


*"Annales  deChimie,"  vol.  23,  p.  51. 

f  "Cyclopaedia  of  Anatomy  and  Physiology,"  vol.  i.,  p.  43,  1835-6. 


COAGULATION    OF    THE   BLOOD  in 

That  fibrin  is  not  present  in  the  blood  before  coagulation 
had  already  been  proved  by  Johannes  Mu'ller  (1831),  but  the 
importance  of  his  observations  was  not  recognised  until 
some  years  later.  Miiller  placed  frog's  blood  (in  which 
the  corpuscles  are  four  times  as  large  as  in  human  blood) 
upon  a  filter-paper  —  after  diluting  it  with  thin  syrup  to 
delay  coagulation.  He  found  that  the  fluid  (plasma)  which 
passed  through  the  filter-paper  completely  unmixed  with 
corpuscles,  clotted  just  as  the  whole  blood  would  have  done. 
Clearly,  therefore,  a  soluble  antecedent  of  fibrin  is  present 
in  circulating  blood.  What  is  the  antecedent,  or  what  are 
the  antecedents,  of  fibrin? 

The  key  to  this  problem  was  provided  by  an  extremely 
ready  observer,  Andrew  Buchanan  (1830),  who  noticed  that 
accumulations  of  inflammatory  lymph,  which  the  surgeon  is 
called  upon  to  "tap,"  sometimes  coagulate  after  removal 
from  the  body  and  at  other  times  do  not.  Searching  for 
the  cause  of  the  clotting,  he  observed  further  that  if  during 
the  operation  a  little  blood  obtains  access  to  it  the  lymph 
clots.  He  therefore  added  to  the  lymph  the  several  con- 
stituents of  the  blood  in  order  that  he  might  ascertain  the 
real  exciting  cause.  He  found  that  the  red  corpuscles  were  ' 
not  necessary,  since  serum  or  even  the  washings  from  a 
blood-clot  would  answer  equally  well.  Indeed,  it  was  not 
necessary  to  use  any  of  the  constituents  of  blood.  It  is  some- 
times found  that  two  exuded  fluids,  such  as  the  lymph  which 
accumulates  in  the  chest  in  pleurisy  and  that  which  accumu- 
lates in  the  abdomen  in  dropsy,  neither  of  which  has  any 
tendency  to  clot  when  left  to  itself,  will  clot  when  mixed 
together.  Coagulation  must  therefore  be  due  to  the  inter- 
action of  two  substances. 

The  problem  now  entered  a  chemical  phase.  Denis  (1859), 
when  investigating  the  proteid  (albuminoid)  constituents  of 
blood,  found  that  if  he  saturated  plasma  (blood  from  which 
the  corpuscles  have  been  removed  before  clotting)  with  sodic 
sulphate,  a  sticky  mass  was  precipitated  which,  when  re- 


H2  AN    INTRODUCTION   TO    SCIENCE 

dissolved  in  pure  water,  gives  a  clot.  This  brings  the  clotting 
property  home  to  the  "globulins'*  in  the  blood,  since  albu- 
min is  not  precipitated  by  sodic  sulphate. 

1861. —  Schmidt,  remembering  Buchanan's  observations, 
resolved  to  obtain  Denis'  "plasmine"  as  two  separate  glob- 
ulins. He  therefore  repeated  the  experiment  upon  each  of 
the  exuded  lymphs,  which  clotted  when  mixed  but  would  not 
clot  separately.  He  obtained  two  globulins  which  he  named 
"fibrinogen"  and  "  fibrinoplastin,"  dissolved  them  sepa- 
rately in  water,  and  found  that  neither  solution  coagulated  ; 
but  fibrin  appeared  when  they  were  mixed.  Proceeding, 
however,  to  obtain  them  by  another  method  in  a  purer  state, 
he  found  that  his  two  globulins,  when  precipitated  by  a 
stream  of  carbonic  acid  gas,  would  not  cause  a  clot,  either 
when  dissolved  separately  or  when  combined.  However, 
some  of  the  washings  of  a  blood-clot  added  to  the  mixture 
caused  it  to  coagulate.  Schmidt  therefore  concluded  that 
three  things  are  needed,  fibrinogen,  fibrinoplastin,  and 
"blood-ferment."  But  in  drawing  this  conclusion  he 
neglected  the  indispensable  scientific  precaution  to  which  we 
have  already  called  attention.  He  overlooked  the  necessity 
for  arranging  a  ' '  control  experiment.' '  Hammersten  showed 
that  Schmidt  might  have  left  fibrinoplastin  out  of  the  mixture. 
When  he  precipitated  it  in  a  pure  state  he  freed  it  from  the 
only  essential  constituent,  the  "ferment."  Fibrinogen,///^ 
ferment,  yields  a  clot.  Fibrinogen  is  dissolved  in  the  plasma, 
and  does  not  become  insoluble  until  it  is  acted  upon  by  the 
so-called  ferment.  The  ferment  is  set  free  on  the  disintegra- 
tion of  the  white  blood-corpuscles  (or  of  some  other  formed 
constituent  of  the  blood);  and  the  reason  for  the  delay  in 
coagulation  which  Hewson  observed,  when  by  ligaturing  a 
vein  in  two  places  he  converted  it  into  a  bag  of  blood,  is 
that  the  corpuscles,  when  kept  in  a  natural  condition,  retain 
their  vitality  for  a  long  time.  With  many  blunders  and  much 
following  of  false  scents  physiologists  have  gradually  traced 
the  blood-clot  to  a  soluble  globulin,  fibrinogen,  which  is 


COAGULATION   OF    THE  BLOOD  113 

changed  into  fibrin  by  the  action  of  a  "ferment."  But  a 
complete  explanation  is  yet  to  seek.  There  are  difficulties 
still  which  need  to  be  cleared  up.  In  the  first  place,  it  is 
known  that  if  all  salts  of  lime  are  removed  from  the  blood  it 
will  not  clot.  Therefore  lime  is  necessary  to 'one  or  other 
of  the  factors.  Either  it  combines  with  the  fibrinogen  at  the 
time  when  it  is  converted  into  fibrin,  which  seems  to  be 
disproved  by  the  fact  that  no  more  lime  can  be  found  in 
fibrin  than  fibrinogen  ;  or  by  uniting  with  an  antecedent  of  the 
ferment  it  develops  the  activity  of  this  substance.  Secondly, 
the  action  of  the  nucleo-proteid  which  is  called  blood-ferment 
differs  widely  from  that  of  the  vast  majority  of  substances 
which  are  classed  as  ferments.  Ferments  are  bodies  which 
induce  changes  in  other  bodies  by  mere  contact,  without 
themselves  taking  part  in  the  chemical  action,  and  the 
change  which  they  induce  is  usually  a  hydrolysis,  or  union 
with  water,  but  fibrin  seems  to  contain  less  water  than  fibrin- 
ogen. Blood-ferment,  like  the  ferment  of  rennet  which 
curdles  milk,  produces  an  insoluble  and  not  a  more  soluble 
substance.  It  is,  however,  possible  that  fibrinogen  is  changed 
by  the  ferment  into  a  substance  containing  more  water  in  its 
molecule,  and  that  this  substance  divides  into  the  insoluble 
fibrin  and  some  other  substance,  probably  a  globulin,  which 
is  freely  soluble.  The  fact  that  the  fibrin  obtained  from  a 
given  quantity  of  fibrinogen  weighs  considerably  less  than 
the  fibrinogen  indicates  that  such  a  cleavage  occurs,  as  it 
undoubtedly  does  in  the  coagulation  of  milk.  Thirdly,  if  the 
formation  of  fibrin  is  due  to  a  reaction  between  fibrinogen 
and  fibrin-ferment  in  the  presence  of  salts  of  lime,  the  injec- 
tion of  fibrin-ferment  into  the  circulating  blood  should 
invariably  produce  coagulation,  whereas  it  usually  fails  to 
bring  about  this  result. 

The  cause  of  the  coagulation  of  the  blood  is  perhaps  the 
oldest  of  physiological  problems.  Its  history  is  typical  of 
the  progress  of  the  science,  and  not  less  characteristic  is  its 
position  at  the  present  time.  Like  most  other  problems,  it 


U4  AN   INTRODUCTION    TO    SCIENCE 

is  almost  but  not  quite  solved,  and  it  is  doubtful  whether 
this  or  any  other  question  which  the  physiologist  is  asked 
can  ever  be  so  answered  as  to  leave  nothing  more  to  say. 
As  knowledge  increases  we  see  farther  into  the  unknown, 
and  each  de*cade  is  less  notable  for  the  questions  which  it 
lays  to  rest  than  for  the  further  questions  to  which  the 
process  of  answering  gives  rise. 


SIR  CHARLES  BELL. 
1774-1842. 


CHAPTER  VII 
The  Functions  of  Nerve-Fibres  and  Nerve-Cells 

ON  the  view  which  we  take  as  to  the  nature  and  amount 
of  control  which  the  nervous  system  exerts  over  the  organs 
depends  to  a  certain  extent  our  conception  of  the  causes 
which  lead  the  organs  to  do  their  work.  There  is  no  other 
problem  in  physiology  of  so  general  a  character  as  this. 
The  simplest  animals  which  exist  at  the  present  time  are 
destitute  of  any  tissue  specially  set  apart  for  the  control  of 
the  other  tissues,  and  it  may  be  assumed  that  the  animals 
which  earliest  appeared  upon  the  earth  were  in  this  respect 
like  the  simplest  animals  now  extant.  The  unicellular 
amoeba  which  crawls  about  the  stalks  of  duckweed  in  our 
ponds  exhibits  in  its  movements  what  in  higher  animals  we 
should  regard  as  evidences  of  purpose.  It  moves  in  the 
direction  of  its  food.  Yet  the  appreciation  of  the  direction 
in  which  food  lies  and  the  guidance  of  its  movements  are 
due  to  the  properties  of  its  general  body-protoplasm,  and 
not  to  any  specialized  internal  structure.  The  simplest 
multicellular  animals,  if  certain  composite  animals  which 
may  be  regarded  as  colonies  of  cells  rather  than  compound 
individuals,  are  excluded,  set  aside  certain  cells  for  the 
reception  of  information  from  the  outer  world,  and  certain 
other  cells,  prolonged  into  fibres,  for  the  transmission  of 
messages  to  its  contractile  tissue.  A  nerve-cell  and  its  fibre 
come  into  existence  in  order  that  they  may  establish  a  com- 
munication between  the  outer  world  and  the  muscle-cells  by 
which  an  animal  moves.  There  is  no  d  priori  reason  why 


n6  AN   INTRODUCTION    TO    SCIENCE 

the  nerve-cell  or  the  nerve-fibre  should  in  any  way  select  or 
elaborate  the  messages  which  it  transmits,  still  less  has  it 
any  antecedent  or  prescriptive  right  to  decide  to  which  of 
all  the  contractile  cells  its  messages  shall  be  delivered. 
Shall  the  type-writing  machine  decide  which  letter  it  will 
write,  or  whether  it  shall  print  it  in  small  type  or  capitals 
when  the  key  marked  m  or  n  is  pressed?  In  its  original 
form  the  nervous  system  is  as  mechanical  in  its  action  as  a 
type-writing  machine.  But  in  the  complex  state  of  organiza- 
tion to  which  it  attains  in  the  higher  animals,  how  far  it 
seems  to  have  advanced  upon  a  mere  arrangement  of  levers 
pressed  down  by  forces  from  the  outer  world  !  And  in  our- 
selves, when  we  study  its  working  by  introspection,  when  we 
feel  it  selecting,  suppressing,  exaggerating,  and  apparently 
originating  the  messages  which  it  transmits,  how  far  it  seems 
to  be  from  an  automatic  machine  played  upon  by  our 
environment.  Herein  lies  the  crux  of  this  great  problem. 
The  animal  is  a  mechanism.  The  animal  has  a  will.  The 
physiologist  who  looks  upon  the  nervous  system  as  a  means 
of  communication  between  sense-organs  and  muscles  is 
content  to  study  its  connections.  The  psychologist  who 
regards  it  as  the  body-tissue  in  which  the  impulses  im- 
pressed upon  the  body  from  the  outer  world  are  "  worked- 
up,"  seeks  for  some  protoplasmic  substance,  which,  owing 
to  its  molecular  instability  and  the  chemical  changes  which 
consequently  occur,  is  capable  of  manufacturing  impulses, 
or  at  any  rate  of  storing  and  profoundly  modifying  those 
which  pass  through  it. 

The  controversy  between  those  who  hold  the  mechanical 
view  and  those  who  incline  towards  the  automatic  theory, 
as  physiologists  would  term  it — meaning  thereby  the  con- 
ception of  the  nervous  system  as  an  originator  of  nerve- 
currents — is  as  old  as  the  science  of  physiology ;  not  that 
we  wish  to  imply  that  the  science  properly  so-called  has  as 
yet  reached  "years  of  discretion."  It  is  useless  to  ask 
when  it  first  assumed  the  exactitude  of  a  science.  We 


NERVE-FIBRES    AND    NERVE-CELLS  117 

must  grant  it  a  nebular  origin.  Descartes  in  the  seventeenth 
century  argues  that  animals  are,  as  we  should  term  them, 
reflex  machines,  incapable  of  feeling  pain,  or,  rather,  of 
knowing  that  they  feel — it  is  very  difficult  to  translate 
Descartes'  metaphysical  theories  into  plain  language.  He 
considered  that  animals  feel,  but,  inasmuch  as  they  do  not 
realise  the  self  which  feels,  they  are  conscious  automata. 
"It  is  my  opinion  that  animals  do  not  see  as  we  see, 
because  we  feel  [know]  that  we  see."  Like  somnambulists 
or  men  in  a  hypnotic  condition,  they  respond,  without 
knowing  it,  to  external  impressions.  Had  Descartes  known 
more  about  the  physiology  of  the  nervous  system  he  would 
have  said  that  all  the  activities  of  animals  were  reflex 
phenomena,  unconscious  responses  to  external  stimuli.  We 
find  the  physiologists  of  twenty  or  thirty  years  ago  inclining 
to  the  opposite  extreme,  and  constructing  a  nervous  system 
out  of  their  own  consciousness,  upon  the  most  approved 
model  of  a  government  department ;  every  little  clump  of 
nerve-cells  an  office  with  a  certain  share  of  authority  and 
well-defined  responsibilities  towards  the  officials  higher  in 
command,  they  imagined  that  they  could  find  the  outer 
world,  as  they  knew  it,  mirrored  in  the  inner  world,  which 
they  did  not  know  ;  and  seeing  that  no  great  administrative 
department  can  work  effectively,  unless  there  be  an  exten- 
sive delegation  of  authority  with  an  equally  elaborate 
system  of  surveillance,  they  allotted  duties  to  various  parts 
of  the  nervous  system  according  to  a  similar  plan.  Their 
"automatic  centres"  for  the  control  of  the  heart  and 
intestines,  the  movements  of  respiration,  etc.,  have  all  been 
shown  the  mere  reflex  mechanisms  which  they  really  are. 
Their  little  dignity  is  denied  them.  They  are  degraded  to  the 
position  of  centres  of  reflex  action,  mere  transmitting 
stations,  that  is  to  say.  Looking  at  the  matter  from  the 
widest  point  of  view,  even  Man  himself  is  a  reflex  machine. 
He  is  kept  awake  by  the  ceaseless  impact  of  external  forces. 
His  running  to  and  fro  is  the  mechanical  effect  which  these 


TiS  AN    INTRODUCTION    TO    SCIENCE 

forces  produce  when,  on  being  passed  through  to  his 
muscles,  they  upset  the  unstable  molecules  of  those  organs. 
The  case  is  recorded  of  a  man  in  whom  disease  of  the 
nervous  system  had  advanced  until  he  was  blind  with  one 
eye,  deaf  with  both  ears,  and  had  lost  cutaneous  sensation. 
One  eye  alone  of  all  his  sense-organs  was  left  to  give  him 
information  of  the  outer  world.  When  this  was  closed  he 
went  to  sleep.  There  can  be  little  doubt,  as  Sir  Michael 
Foster  observes,  that  if  the  brain  were  cut  off  from  all 
external  stimuli,  "volitional  and  other  psychical  processes 
would  soon  come  to  a  standstill,  and  consciousness  vanish." 
If,  therefore,  we  look  at  the  nervous  system  as  a  whole  from 
a  purely  physiological  standpoint— we  have  already  touched 
upon  the  problem  of  consciousness— we  find  it  a  mere  trans- 
mitter of  impulses.  How  much  more  should  we  expect  to 
find  this  true  of  each  separate  nerve-cell  and  its  conduct- 
ing fibre? 

We  will  try  to  give  a  very  brief  historical  sketch  of  the 
problem,  which  for  clearness  we  will  define  as  follows  : 
Does  the  nervous  system  control  the  tissues  in  any  sense 
other  than  that  of  transmitting  to  them  intact  and  unchanged 
the  impulses  which  originate  in  its  terminations  either  on 
the  surface  of  the  body  or  within  the  body  ?  And  since,  as 
we  shall  presently  find,  the  only  element  of  nervous  tissue 
which  can  be  imagined  as  manipulating  messages  in  the 
course  of  their  transmission  is  the  nerve- cell,  the  question 
may  be  reduced  to  this  simple  form— Has  the  nerve-cell  any 
functions  beyond  that  of  providing  for  the  nutrition  of  the 
fibre  which  grows  out  of  it  ? 

The  first  great  step  in  nerve  physiology  was  taken  by  Sir 
Charles  Bell,  when  (in  1811)  he  proved  that  of  the  two^  roots 
by  which  every  spinal  nerve  is  attached  to  the  spinal  cord, 
the  one,  the  posterior,  conducts  sensory  impulses  toward 
the  centre  ;  the  other,  the  anterior,  conducts  motor  impulses 
towards  the  periphery. 

Bell's    discoveries    suggested   various    investigations  to 


NERVE-FIBRES   AND    NERVE-CELLS  119 

Johannes  Miiller  (1832),  the  results  of  which  caused  him 
to  draw  wide  conclusions.  He  pointed  out  that  when  a  man 
receives  a  blow  on  the  eye,  although  the  bruising  of  the 
eyelids  causes  pain,  the  only  message  which  the  optic  nerve 
transmits  is  a  report  to  the  brain  that  stars  have  flashed  their 
light  upon  the  retina  ;  that  when  the  nerve  of  hearing  is 
irritated,  the  patient  hears  a  noise;  that  when  a  nerve  going 
to  a  gland  is  stimulated,  a  flow  of  secretion  follows  ;  or  to  a 
muscle,  contraction  is  induced,  and  so  forth.  The  result  of 
stimulating  a  nerve  is  to  produce  an  effect  of  the  same  kind 
as  that  which  the  impulses  ordinarily  travelling  along  the 
nerve  produce.  So  far  Miiller  was  right,  but  he  generalised 
his  results  in  the  law  of  the  specific  energy  of  nerves,  in 
which  he  wrongly  attributed  the  specific  effects  to  the 
nerves  and  not,  as  we  do  now,  to  the  organs  of  the  brain 
to  which  they  deliver  their  messages.  "A  sensory  nerve 
is  not  merely  a  passive  conductor,  but  each  nerve  from 
an  organ  of  special  sense  possesses  certain  inalienable  forces 
or  qualities  which  the  causes  of  sensations  do  but  excite 
and  render  apparent.  Sensation  is  therefore  the  trans- 
mission to  consciousness,  not  of  a  quality  or  of  a  state  of 
external  bodies,  but  of  a  quality  or  of  a  state  of  our  nerves, 
a  state  to  which  the  external  cause  gives  origin."  "This 
truth,  which  results  from  a  simple  and  impartial  analysis  of 
facts,  not  only  leads  us  to  recognise  that  the  different  sensory 
nerves  are  animated  by  special  forces  independent  of  the 
general  difference  which  distinguishes  them  from  motor 
nerves,  but  also  points  out  the  means  of  setting  physiology 
free  for  ever  from  a  host  of  errors  concerning  the  alleged 
possibility  of  replacing  one  nerve  by  another." 

With  a  view  to  testing  the  truth  of  this  law  of  the  specific 
energy  of  nerves,  many  attempts  were  made  to  make  nerves 
oin  other  trunks  than  their  own.  When  a  nerve  has  been 
divided,  its  cut  ends,  if  they  are  placed  in  contact,  join  again. 
If  it  be  a  motor  nerve,  the  fibres  on  the  central  (cerebro- 
spinal)  side  of  the  injury,  which  are  the  processes  of  cells  in 


120  AN    INTRODUCTION    TO    SCIENCE 

the  spinal  cord,  grow  down  into  the  peripheral  portion  until 
they  find  the  muscle-fibres  from  which  they  have  been 
severed.  If  a  sensory  nerve  be  divided,  its  fibres  also  grow 
centrifugally,  because  they  are  the  processes  of  cells  which 
lie  in  the  spinal  ganglia,  just  outside  the  spinal  cord.  But 
the  attempt  to  cause  the  central  stump  of  a  cut  motor  nerve, 
A,  to  grow  downward  into  the  peripheral  portion  of  a  cut 
sensory  nerve,  B,  is  an  experiment  foredoomed  to  failure. 
Nothing  would  be  gained  by  crossing  two  motor  nerves, 
since  they  both  carry  impulses  of  the  same  kind,  and 
unfortunately  the  nerves  of  special  sense  do  not  allow  of  the 
experiment.  It  is  not  possible,  for  example,  to  cross  the 
nerve  of  taste  with  the  nerve  of  hearing. 

Miiller  was  mistaken  in  attributing  the  specific  effects 
of  stimulating  the  several  sensory  nerves  to  the  nerves 
themselves.  It  was  recognised  by  Vulpian  (1866)  that  "all 
nerves — sensory,  motor,  vaso-motor,  and  others — have  the 
same  properties,  and  are  only  distinct  in  their  functions. 
This  question  is  of  the  highest  importance  for  general 
physiology.  It  dominates  the  whole  physiology  of  nerve- 
fibres."  Many  observations  made  since  Vulpian  wrote  have 
shown  that  a  nerve  has  no  functions  more  specific  than 
those  of  a  telegraph  wire.  It  conducts  impulses.  If  a 
motor  nerve  is  stimulated  in  the  middle  of  its  course  by 
an  electric  current,  a  nerve-current  is  started  braimvards 
(where  it  will  produce  no  effect)  as  well  as  towards  the 
muscles  which  it  supplies  ;  and  the  same  is  true  of  a  sensory 
nerve.  The  specific  effects  depend  upon  the  sense-organ  from 
which  its  message  starts  and  upon  the  receiving  apparatus  to 
which  it  delivers  it.  If  a  telegraph  wire  were  cut  and  the 
sending  apparatus,  or  transmitting  key,  were  moved  from  the 
town  from  which  the  wire  started  to  the  cut  end  of  the  wire, 
the  clerk  in  charge  of  the  indicator  would  suppose  that  any 
message  he  received  came  from  the  town  with  which  the 
wire  ought  to  place  him  in  communication,  and  he  would 
read  his  message  in  this  belief.  That  the  brain  is  in  the 


NERVE-FIBRES    AND    NERVE-CELLS  121 

same  position  is  illustrated  by  a  story  which  Dr.  Hughlings 
Jackson  told  to  the  Neurological  Society  in  his  presidential 
address.  Soon  after  he  had  commenced  practice,  a  patient, 
whose  leg  had  been  amputated,  sent  for  him  in  great  dis- 
tress. "  Doctor,  do  you  know  what  has  become  of  my  leg?" 
"Yes,  it  is  buried  in  old  St.  Pancras  Churchyard." 
"Then,  for  heaven's  sake,  doctor,  have  it  dug  up  and 
scratch  it  just  above  the  ankle." 

Having  shown  that  the  nerve-fibres  are  incapable  of 
tampering  with  the  messages  which  they  transmit,  there 
remains  only  the  grey  matter  of  the  spinal  cord  and  brain. 
This  consists  of  nerve-cells  lying  in  a  plexus  or  feltwork  of 
filaments  derived  from  the  branching  of  the  processes  of 
cells  and  fibres.  This  feltwork  is  of  quite  inconceivable 
richness,  and  it  matters  little  for  our  present  argument 
whether  it  be  a  network  in  the  proper  sense  of  the  word — 
whether  its  filaments  are  continuous  from  fibre  to  cell  and 
vice  versa — or  whether,  as  is  almost  universally  held  at  the 
present  moment,  they  end  freely  and  convey  their  impulses 
across  from  one  filament  to  another  filament  which  lies  near 
to  it,  perhaps  in  contact,  but  not  in  continuity.  At  the 
present  time  almost  all  anatomists  hold  the  "  Neuron 
theory."  They  look  upon  the  elements  of  nervous  tissue  as 
cells,  each  with  one  long  unbroken  process,  the  nerve-fibre 
reaching,  it  may  be,  from  the  spinal  cord  to  the  hand  or 
foot,  and  many  "protoplasmic"  processes  which  branch; 
and  they  consider  that  every  neuron  is  absolutely  uncon- 
nected with  all  other  neurons.  As  the  writer  has  persistently 
opposed  this  theory  since  it  was  first  formulated,  he  had 
better  pass  over  the  question  as  to  the  nature  of  the  nerve 
feltwork  in  silence.  Is  it  the  nerve-cells  or  the  nerve- 
feltwork  which  manipulates  the  messages  which  pass 
through  the  grey  matter  ?  for  all  impulses  pass  through  it. 
It  is  the  tissue  in  which  they  are  redirected  from  sensory 
into  motor  channels.  Several  hypotheses  have  recently 
been  started  to  account  for  the  making  and  breaking  of  the 


122  AN    INTRODUCTION    TO    SCIENCE 

conducting  paths  through  the  grey  matter  ;  the  protoplasmic 
processes  are  supposed  to  retract  and  extend  ;  the  proto- 
plasm of  the  cells  is  supposed  to  flow  out  along  invisible 
nerve-fibres,  and  so  forth  ;  but  no  one  imagines  that  the 
feltwork  of  the  grey  matter  can  in  any  way  alter  the  quality 
of  the  impulses  which  it  transmits. 

If  neither  nerve-fibres  nor  grey  feltwork  exercise  any 
influence  over  the  quality  of  the  impulses  which  they  con- 
duct, the  nerve-cells  alone  remain  to  those  who  wish  to  see 
"the  god  in  the  machine."  And  it  cannot  be  denied  that 
physiologists  have  taken  great  liberties  with  the  machine. 
It  has  turned  out  every  kind  of  work  which  their  fancy 
exacted.  They  have  pictured  the  nerve-cells  as  doing  all 
their  thinking,  and  they  have  thought  of  the  nerve-cells  as 
working  in  the  way  they  pictured.  Reading  some  recent 
text-books  recalls  to  mind  the  Irishman  who  held  up  the 
plank  he  was  sitting  on.  But  as  far  back  as  1877  Lewes 
combated  in  vigorous  language  the  '*  superstition  of  the 
nerve-cell."  Yet,  even  now,  it  is  not  slain.  Perhaps  it 
does  not  deserve  to  die.  Ay,  there's  the  rub  !  Physiology 
is  the  last  of  the  sciences  to  render  itself  independent 
<$  priori  reasoning.  We  feel,  will,  enjoy,  forego,  therefore 
there  must  be  a  mechanism  which  is  capable  of  feeling,  act- 
ing, and,  latest  birth  of  evolutionary  time,  deciding  not  to 
act.  But  this  conclusion  does  not  justify  us  in  assigning 
these  properties  to  the  nerve-cell.  The  physiologist  of  a 
century  ago  said,  with  no  misgivings  as  to  the  cogency  of 
his  argument,  ' '  I  have  come  down  this  morning  in  a  bad 
temper.  Therefore,  my  vital  spirits  are  contaminated.  The 
spleen  is  the  organ  which  makes  black  bile.  Therefore  the 
spleen  has  poured  black  bile  into  my  blood."  Poor  mis- 
understood spleen  !  It  is  busy  day  and  night  in  purifying 
the  blood,  ridding  it  of  its  worn-out  blood-corpuscles. 

All  that  physiologists  know  about  the  nerve-cell  is  that  it 
transmits  impulses  and  provides  for  the  nutrition  of  the 
nerve-fibres  to  which  it  gives  origin.  And  in  connection 


NERVE-FIBRES    AND    NERVE-CELLS  123 

with  the  latter  function  a  curious  point  arises.  By  a  nerve- 
cell,  when  physiologists  and  psychologists  are  assigning  to 
it  its  functions,  is  meant  a  large  nerve-cell,  such  as  occurs  in 
the  anterior  horn  of  the  spinal  cord  or  in  the  cortex  of  the 
brain,  striking  objects  from  which  it  is  difficult  to  divert 
attention.  They  are  so  large  and  so  wonderfully  branching, 
so  picturesque,  with  their  clean  cut  axis-cylinder-process, 
which,  after  giving  off  collateral  branches  in  the  grey 
matter,  runs  an  unbroken  course  perhaps  for  a  yard-length 
in  the  trunk  of  a  nerve,  and  its  protoplasmic  processes 
ramifying  like  the  limbs  and  boughs  of  an  oak  in  winter, 
frosted  with  innumerable  spikelets  known  to  anatomists  as 
"thorns."  It  is  difficult  to  induce  the  members  of  a  his- 
tology class  to  withdraw  their  eyes  from  these  attractive 
structures  or  to  pay  attention  to  any  others  ;  yet,  for  every 
single  large  nerve-cell,  there  are  scores  of  nerve-cells  of 
different  orders,  equally  beautiful  although  extremely 
minute.  What  work  have  they  to  do  ?  The  most  numerous 
of  them,  the  "granules,"  although  they  are  exact  repro- 
ductions in  miniature  of  the  large  nerve-cells,  are  sometimes 
dismissed  as  "connective-tissue  elements,"  even  by 
anatomists  of  the  highest  eminence,  or  as  "  abortive  nerve- 
cells."  Yet  the  only  reason  we  know  why  one  cell  is  big 
and  another  small  is  that  the  one  is  responsible  for  the 
nutrition  of  a  large  fibre  and  the  other  of  a  little  one.  There 
is  no  reason  whatever  for  thinking  that  the  big  cell  has  the 
right  to  modify  the  impulses  which  pass  through  it,  still  less 
to  originate  impulses,  while  the  little  cell  has  no  such 
exalted  prerogative.  Indeed,  we  know  that  some  of  the 
largest  of  nerve  cells,  the  cells  of  the  ganglia  on  the  pos- 
terior spinal  roots,  do  not  in  any  way  modify  the  impulses 
which  pass  through  or  by  them.  If  physiologists  inter- 
preted the  phenomena  which  they  observe  in  their  labora- 
tories in  the  light  of  their  own  science,  without  any  precon- 
ceived notions  as  to  what  they  ought  to  find,  they  would  dis- 
cover no  evidence  that  nerve-cells  possess  any  discriminating 


124  AN   INTRODUCTION   TO    SCIENCE 

power.  All  that  we  learn  from  experimental  evidence  is, 
that  afferent  impulses  are  transmitted  by  the  grey  matter  of 
the  central  nervous  system  into  efferent  channels. 

Physiology  has  passed  through  the  same  stages  as  other 
sciences,  but,  owing  to  the  importance  of  its  applications, 
the  stage  of  a  priori  reasoning  has  been  unduly  prolonged. 
It  began  with  few  facts  and  much  conjecture.  As  knowl- 
edge accumulated  untenable  hypotheses  were  successively 
abandoned  ;  but  theories  took  their  place,  which,  because 
more  detailed,  appeared  to  be  more  true.  Now  it  is  enter- 
ing a  phase  which,  to  borrow  a  term  from  religious  contro- 
versy, may  be  called  agnostic.  We  have  heard  of  the 
automatic  functions  of  nerve-cells,  we  have  seen  the  ner- 
vous system  mapped  out  in  a  multitude  of  little  centres  and 
offices,  upon  a  strikingly  anthropomorphic  plan  ;  but  now 
physiologists  are  beginning  to  acknowledge  that  they  do 
not  know  of  any  function  possessed  by  the  nervous  system 
save  that  of  redistributing  the  forces  which  are  impressed 
upon  the  body  by  the  outer  world.  Truly,  it  has  other 
duties  —  there  is  not  the  least  doubt  about  that  —  but  we  do 
not  know  how  it  performs  them.  Not  a  glimmer  of  light 
has  been  thrown  into  the  mysterious  recesses  in  which  the 
brain  stores  its  presentations  of  sense.  We  know  nothing 
about  the  mechanism  of  memory,  and  memory  is  a  neces- 
sary antecedent  to  any  action  in  which  the  brain  shows 
initiative.  The  work  demanded  of  the  brain  is  of  three 
orders,  (i)  It  redirects  impulses;  (2)  it  stores  impulses 
and,  therefore,  when  it  sets  them  free  again,  it  appears  to 
initiate  them ;  (3)  it  manifests  the  phenomena  of  con- 
sciousness and  volition  which  characterise  or  constitute  the 
ego.  As  yet  experimental  physiology  has  thrown  no  light 
upon  any  process  but  the  first. 

Turning  to  the  handbooks  of  twenty  or  even  ten  years 
ago,  we  find  the  elaboration  of  the  nervous  system  carried 
to  great  lengths.  All  tissues  were  supposed  to  manage  the 
daily  business  of  repair  and  waste,  production  of  an 


NERVE-FIBRES    AND    NERVE-CELLS  125 

"explosive"  metabolite  if  they  are  contractile,  or  of  a 
secernible  metabolite  if  they  are  glandular,  under  the  direct 
supervision  of  nerves  specially  set  apart  for  their  work. 
Physiologists  spoke  of  motor  and  inhibitory,  vaso-constrictor 
and  vaso-dilator,  calorific  and  frigorific,  trophic  nerves, 
glandular  nerves,  etc.,  but  the  search  for  so  many  distinct 
varieties  has  not  been  very  successful.  In  the  case  of  one 
organ,  and  perhaps  of  one  only,  do  we  see  distinct  evidence 
of  its  activity  being  influenced  by  two  antagonistic  nerves. 
The  heart  is  a  most  conscientious  slave.  Seventy  times  a 
minute  or  thereabout  it  beats,  as  long  as  life  lasts,  without 
any  command  from  the  Will.  Its  fault  lies  in  a  slight  incli- 
nation towards  an  excess  of  zeal.  It  is  apt  to  work  too 
hard,  producing  a  pressure  in  the  blood-vessels  which  is  not 
good  for  the  system,  and  leads  to  strain  and  consequent 
dilatation  of  the  heart  itself.  Therefore  we  find  that  while  it 
is  stimulated  to  work  by  slow-acting  and  apparently  not 
very  forcible  sympathetic  nerves,  it  is  restrained  when  nec- 
essary by  a  most  peremptory  "vagus."  If  the  sympathetic 
is  stimulated,  the  result  is  more  work  with  a  diminution  of 
the  heart's  nutritive  balance  —  ?,  e.,  exhaustion.  If  the 
vagus  act,  it  does  less  work  and  its  condition  of  nutrition 
improves.  These  two  nerves  have  been  taken  as  types  of 
two  classes  of  nerves,  the  one  katabolic,  breaking  down ; 
the  other  anabolic,  building  up— the  one  leading  to  the 
diminution  of  the  reserve  of  foodstuffs  in  the  tissues,  the 
other  to  their  accumulation.  There  is  some  evidence,  which 
we  have  not  space  to  detail,  of  the  existence  of  these  two 
sets  of  nerves  in  connection  with  other  organs  ;  but  com- 
paratively few  instances  of  excitement  or  restraint  can  be 
pointed  out  which  are  necessarily  the  direct  results  of 
specific  nerves  and  not  the  indirect  results  of  the  regulation 
of  the  blood-supply  by  vaso-motor  action.  As  Dr.  Langley 
pointed  out  in  his  address  as  President  cf  the  Physiological 
Section  of  the  British  Association  at  Dover,  evolution  is  still 
proceeding,  the  nervous  system  is  making  experiments  ;  all 


126  AN    INTRODUCTION    TO    SCIENCE 

organs  are  not  equally  endowed  with  nerves.  ' '  Since  in  the 
course  of  evolution  a  universal  development  of  motor  nerves 
has  not  occurred,  it  is,  I  think,  to  be  expected  that  the  de- 
velopment of  inhibitory  fibres  should  be  still  less  universal." 
Our  knowledge  of  the  anatomy,  chemistry  and  physiology 
of  the  nervous  system  has  enormously  increased  in  the  last 
few  years,  but  our  conceptions  of  its  relation  to  the  several 
organs  and  tissues  of  the  body  are  far  less  precise  than  they 
used  to  be.  It  is  another  illustration  of  the  tendency  towards 
agnosticism,  and  a  hopeful  sign  of  the  suppression  of  the 
besetting  sin  of  the  physiologist,  who  expects  to  find  every 
part  of  the  body's  work  being  done  as  he  would  order  it  in 
his  house  or  factory  or  laboratory. 

As  a  last  illustration  of  the  direction  in  which  physiologi- 
cal thought  is  trending,  we  may  point  out  that  the  doctrine 
of  the  minute  subdivision  of  functions  among  the  constitu- 
ent parts  of  the  grey  matter  of  the  central  nervous  system 
has  been  rudely  shaken  of  late.  We  have  but  space  for 
three  examples.  And  first,  if  the  reader  will  place  his  finger 
upon  his  pulse  when  he  drinks  a  glass  of  water,  he  will  find 
that  while  he  is  drinking  the  heart  beats  more  quickly. 
This  shows  that  the  impulses  which  pass  through  the 
medulla-  oblongata  and  lead  to  the  inhibition  of  the  heart 
are  checked  during  the  reflex  action  of  swallowing.  The 
carrying  out  of  one  reflex  is  therefore  associated  with  the 
blocking  of  other  reflex  paths.  Secondly,  if  the  reflex 
action  or  pseudo-reflex  action  known  as  the  knee-jerk  is 
properly  investigated,  it  is  found  that  the  passage  of  the 
nerve-current  which  leads  to  this  action  is  affected  by 
events  which  are  occurring  in  far-distant  parts  of  the  central 
nervous  system.  If,  when  a  person  is  sitting  with  his  knees 
crossed  and  the  foot  hanging  free,  the  tendon  below  the 
knee-cap  is  tapped,  say  with  a  paper-knife  or  other  blunt 
object,  the  foot  is  jerked  out  without  any  regard  for  its 
owner's  wishes.  It  is  possible  so  to  arrange  matters  that 
the  tendon  is  tapped  with  a  hammer  worked  by  clockwork 


NERVE-FIBRES    AND    NERVE-CELLS  127 

at  regular  intervals  for  hours  together,  and  at  every  tap  the 
foot  jerks  forward.  And  if,  by  making  the  foot  move  a 
pencil  on  a  travelling  cylinder,  a  record  is  kept  of  the  ampli- 
tude of  the  jerk,  it  is  found  to  vary  not  only  in  harmony 
with  the  subject's  actions,  but  even  with  his  emotions  and 
thoughts.  This  shows  in  a  striking  way  the  interdependence, 
as  opposed  to  the  individualisation,  of  the  several  parts  of 
the  central  nervous  system. 

Thirdly,  we  must  call  attention  to  an  experiment,  recently 
performed,  which  puts  Miiller's  theory  to  a  crucial  test. 
One  nerve  has  at  last  been  made  to  take  the  place  of 
another.  The  nerve  for  the  face,  which  helps  to  regulate 
the  secretion  of  saliva  and  presides  over  blushing,  dilation 
of  the  pupil,  erection  of  the  hairs,  etc. — functions  which  ex- 
plain the  name  of  "little  sympathetic  "  given  to  it  long  ago 
— starts  from  a  ganglion  in  the  upper  part  of  the  neck.  Its 
fibres  therefore  have  their  cells  of  origin  in  this  ' '  superior 
cervical  ganglion"  ;  but  the  messages  which  pass  through 
its  fibres  are  transferred  to  the  ganglion-cells  by  a  long 
nerve,  the  roots  of  which  come  off  from  the  dorsal  part  of 
the  spinal  cord.  The  vagus  nerve  has  been  already  alluded 
to  as  the  nerve  of  the  heart,  the  stomach,  and  certain  other 
viscera.  If  the  nerve  which  passes  up  the  neck  to  the 
superior  cervical  ganglion  is  cut  out,  and  the  vagus  nerve  is 
also  cut  and  turned  round,  the  fibres  of  the  latter  reach  out 
along  the  track  of  the  sympathetic  nerve  until  they  enter  the 
ganglion  and  surround  its  cells  with  their  branches.  Hence- 
forth the  vagus  nerve,  which  ought  to  be  supervising  diges- 
tion and  the  beating  of  the  heart,  controls  blushing,  dilation 
of  the  pupil,  and  the  other  actions  which  formerly  were 
within  the  province  of  the  cervical  sympathetic.  It  is 
unnecessary  to  point  out  how  far-reaching  are  the  conclusions 
to  be  drawn  from  this  experiment.  It  upsets  our  notions  of 
the  specific  functions  of  nerve-centres.  It  throws  doubt 
upon  much  that  has  been  accepted  as  established  knowl- 
edge, and  causes  physiologists  to  pause  and  ask  whether 


128  AN   INTRODUCTION    TO    SCIENCE 

they  may  not  have  devised  a  scheme  of  work  for  the  nervous 
system  on  a  human  pattern,  instead  of  contenting  them- 
selves with  observing  how  it  works. 


CHAPTER   VIII 
Microphytology 

THIS,  the  youngest  of  the  sciences,  already  occupies 
almost  as  much  space  in  the  laboratories  of  the  world  as 
either  of  her  elder  sisters.  So  young  is  she  that  it  is  doubt- 
ful whether  her  parents  have  definitely  agreed  upon  a 
name  as  yet.  Botanists,  pathologists,  chemists  are  anxious 
to  stand  as  sponsors  ;  while  brewers,  dairymen,  indigo  and 
tobacco  manufacturers  and  other  wealthy  men  of  commerce 
are  quite  willing  to  act  as  godfathers  if  the  men  of  science 
will  consent  to  stand  aside. 

The  science  dates  its  birth  from  Pasteur's  researches 
upon  fermentation.  Pasteur  proved  that  fermentation  is 
not  a  chemical  action  in  the  ordinary  sense,  but  the  work 
of  living  cells  which,  in  taking  from  sugar  the  oxygen 
needed  for  their  respiration,  make  such  an  alteration  in  its 
molecule  as  causes  it  to  break  up  into  alcohol  and  carbonic 
acid.  The  amount  of  sugar  which  they  consume  as  food  is 
insignificant  as  compared  with  the  amount  which,  by  their 
vital  activity,  is  decomposed.  It  is  these  bye-actions 
which  characterize  minute  organisms.  They  not  merely 
consume  a  certain  amount  of -the  medium  in  which  they 
live  and  obtain  oxygen  for  its  combustion  from  the  air,  as 
a  larger  plant  or  an  animal  would  do,  but  they  profoundly 
alter  the  constitution  of  the  rest.  For  every  ounce  which 
yeast  adds  to  its  own  weight  when  growing  in  a  solution  of 
sugar,  it  decomposes  about  20  ounces  into  alcohol  and  car- 
bonic acid.  There  are  certain  minute  animals — the  number 

(129) 


130  AN   INTRODUCTION   TO    SCIENCE 

as  present  known  is  very  small — which  produce  effects 
similar  to  those  produced  by  microscopic  plants.  Micro- 
phytology  is  not,  therefore,  an  unexceptionable  name,  but  it 
is  better  than  the  term  bacteriology,  which  is  commonly 
used ;  since  bacteria,  properly  so  called,  are  not  by  any 
means  the  only  organisms  with  which  the  science  deals. 
Some  common  term  is  needed  which  would  imply  that 
minute  organisms  are  studied,  not  on  account  of  the  intrin- 
sic interest  which  attaches  to  their  life-history  as  plants  or 
animals,  but  owing  to  the  importance  of  their  effects. 
And,  judged  by  the  role  which  they  play  in  the  drama  of 
Life,  these  unicellular  things,  invisible  to  the  naked  eye, 
have  an  importance  far  greater  than  that  of  the  large  and 
conspicuous  forms  which  until  recently  have  monopolized 
attention.  Elephants  and  whales,  oaks  and  eucalyptus,  and 
all  other  large  animals  and  plants  might  disappear  without 
any  great  change  in  the  habitableness  of  the  globe ;  whereas, 
if  bacteria  and  moulds  were  to  cease  to  be,  the  surface  of 
the  earth  would  become  incapable  of  supporting  life  of  any 
kind.  Were  it  not  for  these  agents,  which  restore  dead 
plants  and  animals  to  the  soil,  leaves,  as  they  fall,  would 
accumulate  in  a  blanket  impervious  to  the  rootlets  of  ger- 
minating seeds,  and  the  bodies  of  animals  would  dry  up 
until,  in  the  course  of  ages,  they  hid  the  ground  from 
the  sun. 

Microphytology  differs  from  other  sciences,  in  as  much  as 
it  is  studied  not  as  a  pure  science,  but  for  the  sake  of  its 
applications.  As  a  pure  science  it  would  be  a  branch  of 
botany ;  as  applied  science  it  belongs  to  medicine,  as  well 
as  to  various  industries.  Of  the  greatest  importance  to  the 
human  race  is  the  discovery  that  the  entrance  of  microbes 
into  the  body  is  the  true  cause  of  many  diseases,  and  these 
the  most  inimical  to  life.  Again,  coming  within  the  prov- 
ince of  public  health,  it  is  found  that  the  destruction  of 
sewage  is  due  to  the  same  agents.  Hence  the  science  is 
most  ardently  pursued  by  medical  men.  In  commerce  the 


MICROPHYTOLOGY  131 

proper  fermentation  of  wine  and  beer,  and  all  the 
"diseases"  to  which  these  beverages  are  liable,  are  due  to 
microbes.  The  successful  development  of  the  flavour  of 
butter  and  ripening  of  cheese,  the  preparation  of  indigo  and 
the  curing  of  tobacco  depend  upon  the  use  of  the  most 
desirable  kinds  cf  these  minute  organisms.  In  agriculture 
the  reduction  of  nitrogenous  manures  to  a  condition  in 
which  they  can  be  utilized  by  crops,  and  even  the  fixation 
of  free  nitrogen  from  the  air  to  balance  the  waste  due  to  the 
escape  of  nitrogen  into  the  air  and  into  rivers,  is  again  the 
work  of  germs.  They  also  cause  certain  diseases  in  plants. 
Various  other  processes  might  be  named  to  show  how  many 
different  classes  are  interested  in  the  study  of  minute 
organisms,  and  to  explain  the  participation  in  it  of  many 
besides  those  who  first,  and  most  naturally,  undertook  it. 
But  there  is  also  another  reason.  The  investigation  of 
bacteria  requires  very  special  training  in  manipulation  and 
staining,  as  well  as  in  the  use  of  the  microscope,  and  since 
its  importance  is  most  urgent  to  the  students  of  disease,  it 
naturally  follows  that  they  have  acquired  special  skill. 
Hence  the  agriculturist,  the  brewer  and  the  dairyman  come 
to  the  pathologist  for  information  with  regard  to  the  organ- 
isms which  he,  better  than  they,  is  qualified  to  examine. 

The  study  may  be  divided  into  (i)  methods  for  isolating 
and  cultivating  microbes  ;  (2)  the  recognition  of  the  specific 
organisms  which  are  responsible  for  commercial  operations 
and  for  disease,  and  the  elucidation  of  their  life-history ;  (3) 
the  discovery  of  the  reasons  for  their  indirect  and  often 
disastrous  effects,  the  methods  adopted  by  their  hosts  to 
protect  themselves  against  their  action,  and  the  plans  which 
may  be  devised  to  aid  the  host  in  his  warfare  with  the 

germs. 

i.  The  isolation  of  bacteria  is  a  problem  in  gardening  on 
a  very  small  scale.  The  soils  in  which  they  grow  best  are 
gelatin,  agar  (made  from  a  Japanese  seaweed,  and  especially 
valuable  because,  unlike  gelatin,  it  remains  solid  at  blood- 


132  AN    INTRODUCTION   TO    SCIENCE 

heat),  broth,  serum  of  blood,  etc.  Every  housekeeper 
knows  that,  in  summer,  a  calves-foot  jelly  begins  to  liquify 
and  to  give  off  an  unpleasant  odour  within  forty-eight  hours. 
It  is  cultivating  bacteria  on  an  extensive  scale.  Suppose 
that  it  is  desired  to  determine  whether  a  particular  kind  of 
germ  is  present  in  the  air  of  a  London  cowshed,  a  solution 
of  gelatin  is  spread  upon  a  plate  of  glass.  This  is  sterilized 
by  heating  to  a  point  at  which  all  bacteria  are  killed.  It  is 
then  taken  out  of  the  jar  (in  which  it  is  enveloped  by 
sterilized  air),  exposed  for  a  few  minutes  in  the  cowshed, 
and  put  back  into  its  jar.  In  two  or  three  days  the  plate  is 
covered  with  colonies  of  bacteria.  A  gardener's  next 
operation  would  be  the  weeding  of  his  bed.  This  is  im- 
practicable in  microphytology  ;  but  since  the  several  colonies 
have  distinctive  forms,  it  is  possible  to  reverse  the  process 
and,  so  to  speak,  to  "flower"  it.  A  colony,  known  to  be 
of  the  required  kind,  is  transferred  with  a  sterilized  needle 
to  a  tube  of  sterilized  gelatin  and  grown  by  itself.  After 
several  transfers  a  pure  growth  is  obtained  which  may  be 
cultivated,  if  desired,  upon  a  large  scale. 

2.  When  the  pathologist  is  seeking  for  the  specific  germ 
of  a  certain  disease,  he  makes  pure  cultures  of  every  kind  of 
bacteria  which  he  can  obtain  from  the  diseased  animal  or 
person.  If  a  certain  microbe  is  invariably  present,  he  has 
good  ground  for  suspecting  it  of  being  the  cause  ;  but  there 
is  only  one  way  of  proving  that  his  suspicion  is  correct.  It 
must  produce  the  disease  when  injected  into  some  animal 
which  is  capable  of  taking  it.  Having  ascertained  the 
nature  of  the  germ  which  causes  the  disease,  it  next 
becomes  the  duty  of  the  microphytologist  to  investigate  its 
life-history.  There  are  two  points  in  particular  upon  which 
he  needs  to  obtain  information  :  (A )  Can  the  microbe  live 
out  of  the  animal  body,  or  out  of  its  special  medium  ;  and, 
if  so,  is  there  any  situation,  such  as  water  or  the  soil,  in 
which  it  is  commonly  to  be  found  ?  Does  its  life  as  a  para- 
site, that  is  to  say,  alternate  with  a  free  existence?  (B) 


MICROPHYTOLOGY  133 

Does  it  produce  spores,  or  does  it  multiply  by  cell-division 
only? 

A.  The  bacillus  of  tubercle  was  at  first  thought  to  be 
capable  of  a  parasitic  existence  only,  because  it  did  not 
thrive  except  at  temperatures  at  or  near  blood-heat.  It 
has'now  been  found  that,  although  it  does  not  grow  vigor- 
ously unless  at  a  favourable  temperature,  it  can  maintain  a 
torpid  existence  under  more  trying  conditions  than  was 
thought  possible  at  first.  On  the  other  hand,  the  bacillus  of 
lock-jaw  (tetanus)  is,  in  some  localities,  a  common  inhabi- 
tant of  the  soil.  Since  this  terrible  pest  but  rarely  finds  its 
way  into  the  animal  body,  a  most  interesting  problem 
presents  itself.  What  does  the  bacillus  feed  upon  in  the 
soil?  What  relation  do  its  occasional  visits  to  the  animal 
body  bear  to  its  habitual  residence  in  the  soil  ?  Do  myriads 
of  generations  pass  their  lives  in  the  soil  in  order  that,  from 
time  to  time,  a  few  may  be  bred  in  the  body.  We  say  gen- 
erations, although  it  should  be  borne  in  mind  that  these 
unicellular  organisms  are  not  generated,  neither  do  they  die. 
They  merely  divide.  Those  which  are  not  destroyed  by 
outside  agencies  are  immortal. 

As  we  have  already  pointed  out,  the  germs  which  produce 
disease  are  few  in  number  compared  with  those  which  never 
affect  animals  or  Man.  Water  may  teem  with  microbes  and 
yet  be  perfectly  wholesome  to  drink.  Indeed,  in  the  struggle 
for  existence  among  these  minute  organisms  the  more  deli- 
cate "pathogenic"  microbes  usually  go  to  the  wall,  so  that 
the  presence  of  innocent  microbes  in  large  numbers  may 
under  certain  circumstances  be  a  guarantee  that  none 
which  are  noxious  have  had  a  chance  of  survival.  Mic- 
robes are  not  man's  enemies  only,  but  among  the  best  of 
his  friends. 

The  bacteria  which  habitually  live  in  the  soil  produce 
results  compared  with  which  the  effects  of  pathogenic  germs 
are  trifling,  if  living  things  be  looked  at  as  a  whole.  The 
story  of  the  Kentish  farmer  who  boiled  the  rags  which  he 


134  AN   INTRODUCTION   TO    SCIENCE 

used  as  manure  for  his  hops  has  often  been  repeated  of  late 
years.  Fearing  that  the  dirty  rags,  which  at  one  time  were 
invariably  applied  to  hop  gardens,  might  be  a  source  of 
danger  to  his  family  and  labourers,  he  had  them  cooked  in  a 
caldron  before  they  were  dug  into  the  ground  ;  but  found  to 
his  astonishment  that  they  no  longer  acted  as  a  stimulant  to 
the  hops.  The  rags  were  useless  as  manure  when  freed 
from  the  flakes  of  epidermis  and  other  germ-bearing  rem- 
iniscences of  their  sometime  wearers.  Although  this 
story  will  hardly  bear  scientific  criticism,  it  points  a  moral. 
The  soil  is  prepared  for  the  rootlets  of  plants  by  three  sets 
of  bacteria:  (a)  those  which  reduce  organic  matter  to  simple 
salts  which  plants  can  absorb;  (b)  those  which  oxidize 
nitrogenous  (ammonia)  compounds  into  nitrites  and  nitrates ; 
and  (c)  those  which  fix  the  nitrogen  of  the  atmosphere. 
Among  the  most  interesting  of  the  latter  are  the  nitrogen- 
fixing  bacilli  which  grow  in  minute  nodules  on  the  roots  of 
leguminous  plants.  This  life  is  an  illustration  of  genuine 
symbiosis,  the  bacteria  being  housed  by  the  higher  plant  in 
specially  made  excrescences,  for  the  sake  of  the  services 
which  they  are  able  to  render  in  return.  The  nodules  on 
the  root  of  a  pea  are  easily  seen  even  without  a  lens.  If 
one  of  them  is  cut  a  creamy  fluid  escapes,  which  is  found 
upon  microscopic  examination  to  be  loaded  with  bacilli. 
How  the  bacilli  do  their  work  has  not  been  ascertained  as 
yet,  but  it  is  certain  that  they  fix  the  nitrogen  of  the  air 
which  circulates  in  the  interstices  of  the  soil.  Farmers  have 
long  known  that  peas,  .vetches  and  clovers,  better  than  any 
other  crops,  prepare  the  land  for  wheat.  They  were  aware, 
too,  of  the  importance  of  well  stirring  the  soil  to  admit  air. 
Now  that  the  explanation  has  been  found,  it  is  probable  that 
scientific  agriculture  will  discover  means  of  replacing  the 
nitrogen  which  is  constantly  escaping  from  the  soil,  without 
recourse  to  artificial  manures.  Experiments  have  been  made 
on  a  large  scale  in  Germany  in  cultivating  nitrogen-fixing 
bacilli  and  introducing  them  with  the  seed.  The  use  of  these 


MICROPHYTOLOGY  135 

cultures  has  not,  however,  given  good  results  in  England 
up  to  the  present  time. 

B.  From  a  practical  point  of  view  it  is  very  important 
to  ascertain  whether  a  microbe  produces  spores.  A  tem- 
perature of  70°  C.  kills  all  microbes ;  whereas  boiling  is 
required  to  kill  their  spores.  The  spores  can  also  resist 
dessication  and  oxidation  far  better  than  bacteria.  The 
microbes  of  plague,  diphtheria  and  pneumonia  do  not  form 
spores. 

3.  It  has  already  been  stated  that  most  diseases  are 
caused  by  microbes.  They  produce  not  only  various  fevers, 
but  cholera,  tetanus,  leprosy,  tuberculosis,  etc.,  in  which  a 
febrile  temperature  is  not  the  most  marked  symptom.  At 
present  they  are  being  studied  chiefly  for  the  sake  of  finding 
out  how  they  cause  disease,  and  how  both  men  and  animals 
may  be  rendered  insusceptible,  or  able  to  combat  the  disease 
if  they  cannot  be  prevented  from  taking  it.  To  what  are 
the  ill-effects  which  follow  an  invasion  by  bacteria  due? 
They  are  certainly  not  due  to  the  demand  made  by  the 
microbes  upon  nutrient  fluids  or  tissues  of  the  body,  but  to 
poisons,  called  collectively  toxins,  which  they  either  secrete 
or  cause  the  tissues  to  secrete.  The  secretion  of  the 
microbes  may  be  a  virulent  and  speedy  poison,  or  it  may  act 
indirectly,  leading  to  decomposition  of  the  body  cells  and 
juices,  with  consequent  formation  of  poisonous  substances. 
In  diphtheria,  for  example,  the  bacilli  live  in  the  mucous 
membrane  of  the  throat.  The  substances  which  they  pro- 
duce resemble  ferments  in  many  ways,  particularly  in  their 
sensitiveness  to  heat.  Although  not  poisonous  in  them- 
selves, these  ferments,  when  absorbed  into  the  blood,  induce 
the  formation  of  poisons  to  which  all  the  constitutional 
symptoms  are  due.  After  the  patient  has  recovered  from 
the  local  symptoms  in  the  throat  he  may  succumb  to  the 
degeneration  of  his  nervous  system  which  the  toxins  set  up. 
What  the  microbe  gains  by  destroying  its  host  is  a  problem 
as  yet  unsolved.  It  seems  like  a  premature  attempt  to  carry 

J 


136  AN   INTRODUCTION   TO    SCIENCE 

out  the  great  mission  of  bacteria  in  returning  all  organized 
beings  to  the  soil. 

In  the  struggle  with  its  invaders  the  organism  wins  in  the 
long  run  ;  but  myriads  of  individuals  die  before  immunity  to 
any  form  of  disease  is  acquired  by  the  race.  The  progress 
which  is  being  made  towards  the  acquisition  of  a  power  of 
resisting  disease  is  strikingly  shown  in  the  innocence  of 
measles  among  the  white  races  compared  with  their  viru- 
lence when  introduced  into  the  South  Sea  Islands  and  other 
places  where  they  were  previously  unknown.  No  diseases 
are  restricted  to  definite  geographical  areas  in  these  days  of 
free  communication  ;  but  there  is  evidence  that  even  within 
historic  times  the  evolution  of  human  beings  has  tended  to 
protect  them  against  those  forms  of  germ  to  which  they 
were  especially  exposed,  while  the  evolution  of  the  germs 
has  resulted  in  the  production  of  new  forms  of  disease. 

The  animal  body  counteracts  the  toxins  which  microbes 
produce  by  developing  within  its  tissues  and  juices  a  class 
of  substances  to  which  the  collective  name  of  antitoxins  has 
been  given.  Take  diphtheria  as  an  example.  When  a 
susceptible  animal,  such  as  the  horse,  is  inoculated  with  the 
diphtheria  toxin  it  exhibits  symptoms  of  the  disease.  If  the 
dose  is  small  the  horse  recovers.  After  an  interval  (of  say 
five  days)  a  larger  dose  of  the  toxin  is  required  to  produce 
disturbance.  Eventually,  an  unlimited  dose  may  be  given 
without  effect.  It  is  immune  because  its  blood  is  charged 
with  antitoxin.  And  now,  if  some  of  its  blood-serum, 
which  has  been  perfectly  sterilized  so  that  it  will  keep  for 
weeks  or  months,  is  injected  beneath  the  skin  of  a  child 
suffering  from  diphtheria,  the  antitoxins  of  the  horse  rein- 
force those  which  the  child  is  making  for  itself  and  enable 
it,  if  the  case  has  not  advanced  too  far,  to  antidote  the 
toxins  of  the  disease. 

Vaccination  confers  immunity  in  a  somewhat  different 
way.  For  some  reason,  which  is  not  as  yet  satisfactorily 
explained,  after  ooe  invasion  of  a  particular  kind  of  germ 


MICROPHYTOLOGY  137 

the  subject  is  proof  against  further  attacks.  A  second 
attack  of  small-pox  is  very  rare.  Persons  who  have  had 
tuberculous  glands  in  youth  seldom  contract  tuberculosis  of 
the  lungs.  Typhoid  fever,  scarlet  fever,  chicken-pox,  etc., 
may  attack  a  second  time,  but  the  second  attack  is  not 
likely  to  do  much  harm.  For  more  than  a  century  people 
preferred  to  inoculate  themselves  with  small-pox,  securing  a 
mild  attack  when  the  system  was  not  predisposed  to  the 
disease,  rather  than  run  the  risk  of  an  attack  under  unfa- 
vourable circumstances;  but  <( Variolation"  was  prohib- 
ited by  Act  of  Parliament  in  1840  because  the  inoculated 
person  was  a  focus  of  the  disease.  Although  he  might 
secure  a  mild  attack  for  himself,  he  was  just  as  liklyasany 
other  small-pox  patient  to  distribute  the  disease  in  a  virulent 
form  to  his  attendants.  In  1796  Jenner  made  the  great 
discovery  that  inoculation  with  small-pox  which  had  passed 
through  the  body  of  a  cow  (an  animal  which  is  compara- 
tively immune),  and  had  thus  become  attenuated,  produced 
a  mild  attack  of  "cow-pox,"  which  is  a  perfect  protection 
against  small-pox,  although  the  person  so  affected  cannot 
spread  the  unattenuated  disease. 

In  the  treatment  of  hydrophobia  the  virus  is  attenuated  in 
a  different  way.  The  spinal  cord  of  a  rabbit  which  has 
died  of  the  disease  is  dried.  A  broth-culture  is  made  from 
the  dried  cord  and  the  patient  is  inoculated  with  this.  He 
is  thus  rendered  immune  before  the  attack  of  hydrophobia 
has  had  time  to  supervene.  Fortunately,  a  long  interval 
elapses  between  the  bite  and  the  development  of  the  disease. 
The  same  treatment  would  probably  be  applicable  to  lock- 
jaw if  it  were  possible  to  ascertain  that  the  germs  had  been 
introduced  into  a  wound.  Cholera  is  anticipated  and  dis- 
armed by  inoculating  a  person  with  a  culture  of  the  cholera- 
spirillum  which  has  been  weakened  by  cultivation  in  broth  or 
agar.  Plague  is  stayed  by  introducing  into  the  system  of 
those  who  have  not  yet  been  attacked  a  sufficient  dose  of 
plague-toxins  prepared  from  a  culture  of  the  bacillus  which 


138  AN   INTRODUCTION    TO    SCIENCE 

has  been  killed  by  heat.     The  inoculations  just  described 
illustrate  four  different  methods  of  securing  immunity. 

How  it  is  the  antitoxic  results  of  an  invasion  remain  in 
the  system  for  years  after  the  germs  have  been  defeated  is  a 
problem  which  still  awaits  solution.  It  seems  impossible 
that  the  antitoxins  formed  at  the  time  of  an  attack  should  be 
stored  for  long.  Rather  must  \ve  suppose  that  the  tissues 
are  in  some  way  trained  to  produce  them  as  required.  For 
a  long  time  pathologists  have  looked  upon  the  white  blood- 
corpuscles  or  leucocytes  as  the  body's  medical  officers  of 
health.  Undoubtedly  they  have  the  power  of  catching  and 
devouring  germs  or  any  other  foreign  particles  which  may 
force  admittance.  Their  independent  existence,  and  the 
situation  of  their  camps,  points  them  out  as  Nature's  police. 
Their  breeding  grounds  are  the  tonsils  at  the  entrance  to  the 
throat,  the  submucous  tissue  of  the  wind-pipe  and  bronchi, 
Peyer's  patches  in  the  intestine,  the  glands  of  the  neck,  the 
armpit,  and  the  groin,  which  guard  the  outflows  of  lymphatic 
vessels  and  bar  the  passage  into  the  blood-stream  and  the 
vital  organs.  When  the  throat  is  sore  the  tonsil  enlarges, 
and  the  leucocytes  can  be  seen  to  sweep  down  from  their 
fortress,  to  work  their  way  among  the  cells  of  the  mucous 
membrane,  and  even  to  reach  its  surface  in  their  eagerness 
to  give  battle  to  any  noxious  germs  which  might  try  to  force 
an  entrance  into  the  connective  tissue  which  lies  beneath  it. 
They  patrol  the  blood-vessels  to  the  number  of  about  one 
leucocyte  for  every  three  hundred  red  blood-corpuscles ; 
now  rolling  down  the  blood-stream,  now  clinging  to  the 
vessel-wall  and  squeezing  themselves  between  its  lining 
cells  in  search  of  effused  blood  or  broken-down  tissue  which 
would  set  up  mischief  if  not  speedily  removed.  They  are 
entirely  independent  of  nervous  control,  are  as  free  to 
wander  within  the  body  as  an  amceba  in  a  pond.  The  best 
of  our  nutrient  juices  are  at  their  command.  They  are  fed 
as  no  fixed  tissue-cells  are  fed.  And  in  return  for  this  hospi- 
tality they  do,  as  far  as  we  know,  no  work,  save  that  of  re- 


MICROPHYTOLOGY  139 

moving  dead  or  foreign  particles.  Our  contract  with  them 
resembles  that  made  by  the  Saxons  with  the  Danes.  They 
are  free  to  take  what  tojl  they  choose  so  long  as  they  protect 
us  against  all  other  robbers.  Serum  which  contains  anti- 
toxins is  equally  effective  whether  leucocytes  be  present  or 
no  ;  but  it  is  not  improbable  that  the  leucocytes  add  to  their 
services  in  catching  germs  the  further  service  of  secreting 
antitoxins.  It  may  be  that  in  some  incomprehensible  way  a 
successful  invasion  trains  them  to  resist  in  future  the  strategy 
of  the  invading  host. 

A  few  words  must  be  added  with  regard  to  the  methods 
which  everyone  may  adopt  to  prevent  the  entrance  of  bacteria. 
At  a  reception  in  Vienna  it  was  said  of  Lord  Lister  that  he 
had  saved  more  lives  than  the  Franco-German  War,  then 
recently  ended,  had  sacrificed.  But  antiseptics  incompletely 
carried  out  are  worse  than  no  antiseptics  at  all.  Microbes 
can  pour  through  a  pin-prick  in  a  sheet  of  paper  faster  than 
rats  through  a  barnyard  gate.  Their  extreme  minuteness — 
they  average,  perhaps,  about  three  or  four  hundredths  of  a 
millimetre  in  length  by  less  than  one  thousandth  of  a  milli- 
metre in  breadth — makes  it  extremely  difficult  to  keep  them 
out.  When  they  find  admittance  their  effects  are  extra- 
ordinarily certain.  Fifty-seven  houses  in  Bristol  were 
supplied  by  milk  which  came  from  a  farm  where  the  milk- 
cans  were  washed  in  water  contaminated  by  typhoid  germs. 
Typhoid  fever  broke  out  in  forty-one  of  these  houses.  In 
India  it  has  happened  more  than  once  that  every  person 
who  partook  cf  cholera-infected  food  has  been  attacked  with 
the  disease.  There  is  no  limit  to  the  care  which  must  be 
taken.  At  a  certain  officer's  quarters  every  hygienic  pre- 
caution which  could  be  thought  of  was  adopted.  The 
servants  were  not  allowed  as  they  came  home  from  the 
laundry  to  leave  the  camp.  Serviettes  and  table-cloths  were 
carefully  disinfected  ;  but  the  native  servants  rinsed  the  dish- 
cloths in  an  infected  stream.  A  jelly  was  set  in  a  carefully 
cleaned  mould,  and  all  who  partook  of  it  were  attacked  by 


140  AN   INTRODUCTION   TO    SCIENCE 

cholera.  There  is  such  a  thing  as  mischievous  cleanliness. 
It  looks  so  immaculate  that  it  withdraws  attention  from  the 
real  source  of  danger. 

Fortunately,  there  is  a  treatment  to  which  all  microbes 
are  ready  victims.  They  are  easily  killed  by  heat.  None 
can  survive  a  temperature  of  70°  C.,  and  boiling  destroys  all 
kinds  of  spore.  A  boiled  bacillus  is  an  insignificant  thing ; 
but  a  live  germ  is  more  to  be  feared  than  a  dead  lion. 


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